Genome Sequence and Comparative Genomics Analysis of a Vibrio cholerae O1 Strain Isolated from a Cholera Patient in Malaysia

The genome sequence analysis of a clinical Vibrio cholerae VC35 strain from an outbreak case in Malaysia indicates multiple genes involved in host adaptation and a novel Na⁺-driven multidrug efflux pump-coding gene in the genome of Vibrio cholerae with the highest similarity to VMA_001754 of Vibrio mimicus VMA223.     

云南山楂茎尖的离体培养及其无性系快速繁殖

用云南山楂(Crataegus scabrifolia(Franch.)Rehd.)成年树茎尖和实生芽两种不同发育阶段的材料为外殖体,诱导它们休眠芽萌动,丛生芽条并诱导芽条生根。实验结果如下:1.以成年态的云南山楂侧芽为外植体,培养在附加IAA 0.1—0.5mg/l+6-BA 1-2mg/l的MS培养基上可诱导芽的萌发;将芽继代培养在附加0.5—1mg/l 6-BA的SH或MS培养基上,40天后芽数增殖4—6倍;将芽条截下置于1/2MS培养基上,附加不同浓度的IAA或IBA,可得到50—80％的生根率。2.以实生芽为外殖体,在相同条件下,则20天后芽数增殖便可获4—6倍;98％以上生根。结果表明:云南山楂的幼年态要比成年态易脱分化和再分化。     

香荚兰种子的无菌萌发试验

香荚兰(Vanilla planifolia)是兰科、香荚兰属植物,主产于湿热地区。香荚兰的果实是国际上重要的食用香料的原料。大约在1960年,我国引入香荚兰试栽。生产上,通常用扦插法繁殖;但如用种子繁殖,虽然结实较晚(约7至8年开始结实,较扦插苗晚4—5年),但结实期长,盛产期可维持约15年。而且,在杂交育种过程中,一定要用种子繁殖。     

N6-substituted 9-methyladenines: a new class of adenosine receptor antagonists

A series of 15 N6-substituted 9-methyladenines have been assessed as antagonists of A2-adenosine receptor-mediated stimulation of adenylate cyclase in membranes of human platelets and rat PC12 cells and of A1-adenosine receptor-mediated inhibition of adenylate cyclases in membranes of rat fat cells and as inhibitors of binding of N6-R-[3H]phenylisopropyladenosine to A1-adenosine receptors in rat brain membranes. N6 substitution can markedly increase the potency of 9-methyladenine at A1 receptors, while having lesser effects or even decreasing potency at A2 receptors. Effects of N6 substituents on adenosine receptor activity of the 9-methyladenines are reminiscent of effects of N6 substituents on activity of adenosine, suggesting that N6 substituted 9-methyladenines bind to adenosine receptors in the same orientation as do N6-substituted adenosines. N6-Cyclopentyl-9-methyladenine with Ki values at the A1 receptors of 1.3 microM (fat cells) and 0.5 microM (brain) is at least 100-fold more potent than 9-methyladenine (Ki 100 microM, both receptors), while at the A2 receptors KB values of 5 microM (platelets) and 25 microM (PC12 cells) make it 5-fold more potent and equipotent, respectively, compared to 9-methyladenine (KB 24 microM, both receptors). N6-Cyclopentyl and several other N6-alkyl and N6-cycloalkyl analogs are selective for A1 receptors while 9-methyladenine is the most A2 receptor selective antagonist. The N6-R- and N6-S-(1-phenyl-2-propyl)-9-methyladenines, analogous to N6-R- and N6-S-phenylisopropyladenosines, exhibit stereoselectivity at both A1 and A2 receptors. Marked differences in potency of certain N6-substituted 9-methyladenines at the A2 receptors of human platelets and rat PC12 cells provide evidence that these are not identical receptors.     

Isolation and characterization of a Mr = 110,000 glycoprotein localized to the hepatocyte bile canaliculus

A Mr = 110,000 glycoprotein, GP 110, was partially purified using wheat germ agglutinin-Sepharose affinity chromatography from a bile canalicular-enriched membrane fraction denoted N2u of rat liver. This fraction was subjected to preparative sodium dodecyl sulfate-polyacrylamide gel electrophoresis and the Mr = 110,000 polypeptide was excised and used as an immunogen in rabbits. The antisera were found to specifically recognize a Mr = 110,000 polypeptide, named GP 110, in the N2u membrane fraction. In isolated hepatocytes, GP 110 was readily accessible to cell surface iodination catalyzed by lactoperoxidase at 4 degrees C and was judged by immunoprecipitation studies to contain about 2% of total radioactivity incorporated into externally oriented proteins of the cell. Immunoprecipitated GP 110 was shown by two-dimensional polyacrylamide gel electrophoresis to migrate with an approximate pI of 4.9. Indirect immunofluorescence on frozen liver sections demonstrated that GP 110 was primarily localized in the bile canaliculus. In corroborative studies employing subcellular fractionation, it was found that GP 110 was enriched nearly 19-fold in P2, a plasma membrane fraction primarily derived from the sinusoidal domain, and 44-fold in N2u. In contrast, only low levels of GP 110 were present in endoplasmic reticulum, mitochondrial, cytosolic, and nuclear-enriched fractions of liver. The physiological function of GP 110 is as yet unknown; antisera to it did not immunoprecipitate other known bile canalicular proteins of similar molecular weights. GP 110 was found to be extensively glycosylated relative to other known membrane proteins; approximately 33% of the apparent molecular weight appear to be carbohydrate. In agreement, limited removal of N-linked carbohydrate chains indicated that there are approximately eight chains/GP 110 polypeptide. Neuraminidase treatment of GP 110 resulted in a desialylated Mr = 85,000 polypeptide suggesting that the majority of carbohydrate chains on GP 110 are of the complex type.