The ars operon of Escherichia coli confers arsenical and antimonial resistance.

The chromosomally encoded arsenical resistance (ars) operon subcloned into a multicopy plasmid was found to confer a moderate level of resistance to arsenite and antimonite in Escherichia coli. When the operon was deleted from the chromosome, the cells exhibited hypersensitivity to arsenite, antimonite, and arsenate. Expression of the ars genes was inducible by arsenite. By Southern hybridization, the operon was found in all strains of E. coli examined but not in Salmonella typhimurium, Pseudomonas aeruginosa, or Bacillus subtilis.     

Effects of multicopy LeuO on the expression of the acid-inducible lysine decarboxylase gene in Escherichia coli.

We previously reported that mutations in hns, the structural gene for the histone-like protein H-NS, cause derepressed expression of cadA, which encodes the acid-inducible lysine decarboxylase at noninducing pH (pH 8.0). This study reports the characterization of a plasmid isolated from an Escherichia coli library that suppresses the effect of an hns mutation on cadA expression. A previously sequenced open reading frame, leuO, proves to be the gene that causes the hns-complementing phenotype. The mechanism for this phenotype appears to be overexpression of leuO from a multicopy plasmid, which drastically reduces production of CadC, the essential activator for cadA induction. These results show an in vivo regulatory phenotype for leuO, consistent with its proposed protein sequence.     

Nonlinear sequence-dependent structure of nigral dopamine neuron interspike interval firing patterns.

Firing patterns of 15 dopamine neurons in the rat substantia nigra were studied. These cells alternated between two firing modes, single-spike and bursting, which interwove to produce irregular, aperiodic interspike interval (ISI) patterns. When examined by linear autocorrelation analysis, these patterns appeared to reflect a primarily stochastic or random process. However, dynamical analysis revealed that the sequential behavior of a majority of these cells expressed "higher-dimensional" nonlinear deterministic structure. Dimensionality refers to the number of degrees of freedom or complexity of a time series. Bursting was statistically associated with some aspects of nonlinear ISI sequence dependence. Controlling for the effects of nonstationarity substantially increased overall predictability of ISI sequences. We hypothesize that the nonlinear deterministic structure of ISI firing patterns reflects the neuron's response to coordinated synaptic inputs emerging from neural circuit interactions.     

唐菖蒲周年供花研究初报

本文报道唐菖蒲花期调节试验的结果,表明采用自然栽培、控制栽培及促成栽培等综合措施是实现唐菖蒲周年供花的有效途径     

Antitumor agents-CLXXV. Anti-tubulin action of (+)-thiocolchicine prepared by partial synthesis

(+)-Thiocolchicine (2b) was prepared from (±)-colchicine (1) in a five-step reaction sequence that included chromatographic separation of appropriate camphanylated diastereomers. Acid hydrolysis of the (+)-diastereomer, followed by acetylation, yielded the desired product 2b. (+)-Thiocolchicine has 15-fold lower inhibitory activity against tubulin polymerization than (−)-thiocolchicine, and is 29-fold less potent for inhibiting growth of human Burkitt lymphoma cells. The enantiomer 2a, prepared from the (−)-camphanylated diastereomer, had potent activity in all assays comparable to that of (−)-thiocolchicine prepared by other methods. These results support the hypothesis that the proper configuration of colchicine-related compounds is an important requirement for their anti-tubulin action.     

载脂蛋白AⅡ保护内皮细胞的实验研究

以细胞形态观察、细胞存活率、乳酸脱氢酶释放和前列环素测定等方面研究载脂蛋白AⅡ保护内皮细胞的作用.结果显示,载脂蛋白AⅡ可部分拮抗低密度脂蛋白对内皮细胞的损伤作用, 维持内皮细胞形态基本正常,乳酸脱氢酶释放减少,前列环素合成增加.     

鳞木目小孢子叶球山西鳞孢穗（新种）的解剖特征

描述了山西太原西山煤田太原组７号煤层煤核中一种鳞木目的小孢子叶球——山西鳞孢穗（新种）（Ｌｅｐｉｄｏｓｔｒｏｂｕｓｓｈａｎｘｉｅｎｓｅ ｓｐ． ｎｏｖ．）。其主要特征是：孢子叶球较小,长３．５ ｃｍ 以上,直径１．６～１．８ ｃｍ 。轴具管状中柱,孢子叶螺旋状着生于轴上。孢子叶柄长６～７ ｍ ｍ ,远端叶片长１．２ ｃｍ 以上。孢子叶柄具翅,翅长２～２．５ ｍ ｍ 。小孢子囊可能呈袋形,长与孢子叶柄相近,宽约４．５ ｍ ｍ ,高２～３ ｍ ｍ ,以其长度的约２／３着生于孢子叶柄的腹面上。成熟的孢子囊壁仅由一层柱状细胞构成。小孢子直径６８～７７ μｍ ,具三缝,远极面具短刺     

Characterization of a plasma membrane-associated phosphoinositide-specific phospholipase C from soybean

Phosphoinositide-specific phospholipase C (PI-PLC) is a key signal transducing enzyme which generates the second messengers inositol trisphosphate and diacylglycerol in mammalian cells. A cDNA clone (PI-PLC1) encoding a phosphoinositide-specific phospholipase C was isolated from soybean by screening a cDNA expression library using an anti-(plasma membrane) serum. Genomic DNA gel blot analysis suggested that the corresponding gene is a member of a multigene family. The deduced amino acid sequence of the soybean PI-PLC1 isozyme contains the conserved X and Y regions, found in other PI-PLCs. It is closely related to mammalian δ-type PI-PLCs, Dictyostelium discoideum PI-PLC and yeast PI-PLC1 in terms of the arrangement of the conserved region. Unlike mammalian δ-type PI-PLCs and yeast PI-PLC1, the putative Ca²⁺-binding site of the soybean PI-PLC1 is located in the region spanning the X and Y domains, and the N-terminal region is truncated. FLAG epitope-tagged PI-PLC1 fusion protein purified from transgenic tobacco plants showed phosphoinositide-specific phospholipase C activity. Heterologous expression of the soybean PI-PLC1 cDNA in a yeast PI-PLC1 deletion mutant complemented the lethality phenotype of haploid PI-PLC1 disruptants. Immunoblot analysis of the cell fractions prepared from transgenic tobacco plants over-expressing the FLAG epitope-tagged PI-PLC1 fusion protein indicated that the protein encoded by the PI-PLC1 cDNA was localized in the cytosol and plasma membrane.