New taxa and combinations in Old World Urticaceae

In anticipation of the publication of full revisions, a diagnosis of a new species of Droguetia is presented together with two new combinations for subspecies of Droguetia iners , a new combination for a species and a variety on Didymodoxa and a new combination for a subspecies of Australina pusilla . The name Elatostema trinerve Hochst. (1845) is shown to be conspecific with and antedate Urera cameroonensis Wedd. (1869). The new combination Urera trinervis is therefore made.     

荔枝胚胎败育与酚类抑制物质的关系

在荔枝 (LitchichinensisSonn .)胚胎败育发生期 ,以系统溶剂法从正常或败育胚珠中初步提取酚类抑制物质 ,通过TLC分离与纯化 ,用GC MS联用仪进一步分离鉴定 ,并以标准品核对。试验首次从荔枝胚珠中分离鉴定出酚类抑制物质对羟基苯甲酸 (p_HBA)。生物活性测定表明 ,p_HBA是一种很强的生长抑制物质。在败育胚珠中其含量及IAA氧化酶活性均显著高于正常胚珠 ,IAA水平则明显低于正常胚珠 (P <0 .0 1)。因此认为 ,p_HBA参与了荔枝胚胎发育的调节 ,高含量的p_HBA是通过促进IAA侧链的氧化并影响促进和抑制生长的物质之间的平衡而导致荔枝胚胎的败育     

HeLa细胞端粒酶最适反应条件及活性重建

端粒是真核细胞染色体末端的重复ＤＮＡ序列 ,其生物学功能是防止染色体ＤＮＡ降解、末端融合、非正常重组和染色体的缺失[1] .由于存在“末端复制问题” ,随着老化人体细胞端粒重复序列长度不断缩短 ,但在生殖细胞中由于端粒酶的存在 ,端粒序列并不缩短 .端粒酶是由蛋白质和ＲＮＡ构成的核蛋白 ,是依赖ＲＮＡ的ＤＮＡ聚合酶 ,在ＤＮＡ3’端合成端粒重复序列[2 ] .研究表明 ,在 85 %～ 95 %的人肿瘤细胞中可以检测到端粒酶的活性[3 ,4 ] ,而在正常体细胞中除生殖细胞和造血干细胞等极少数细胞中存在端粒酶活性外 ,均检测不到端粒酶活性 ,这…     

Inhibition of IFN-gamma signaling by glucocorticoids

Recent reports suggest that a novel mechanism of glucocorticoid (GC) immunosuppressive action is inhibition of signaling by IL-2 and IL-12, cytokines that use the Janus kinase-STAT signaling pathway. We investigated whether GCs could also block activation of Janus kinase-STAT signaling by IFN-gamma, a potent proinflammatory cytokine. Addition of dexamethasone to PBMC cultures resulted in a dramatic inhibition of IFN-gamma activation of STAT1. Several days of exposure to GCs were required for inhibition of IFN-gamma signaling to become apparent, and the underlying mechanism was down-regulation of STAT1 expression. GCs suppressed the expression of STAT1 mRNA, but did not affect STAT1 protein stability. STAT1 expression and IFN-gamma signaling were preferentially suppressed in macrophages. GCs did not act directly on macrophages, but worked indirectly by regulating macrophage-lymphocyte interactions that control STAT1 expression. GCs inhibited IFN-gamma-inducible gene expression, thus demonstrating the physiological significance of inhibition of signal transduction. Our results identify a novel level of regulation of IFN-gamma signaling, whereby GCs control the amplitude of IFN-gamma signaling by regulating STAT1 expression. These results suggest that inhibition of IFN-gamma signaling contributes to the immunosuppressive action of GCs.     

Inhibition of IL-6 and IL-10 signaling and Stat activation by inflammatory and stress pathways

The development and resolution of an inflammatory process are regulated by a complex interplay among cytokines that have pro- and anti-inflammatory effects. Effective and sustained action of a proinflammatory cytokine depends on synergy with other inflammatory cytokines and antagonism of opposing cytokines that are often highly expressed at inflammatory sites. We analyzed the effects of the inflammatory and stress agents, IL-1, TNF-alpha, LPS, sorbitol, and H(2)O(2), on signaling by IL-6 and IL-10, pleiotropic cytokines that activate the Jak-Stat signaling pathway and have both pro- and anti-inflammatory actions. IL-1, TNF-alpha, and LPS blocked the activation of Stat DNA binding and tyrosine phosphorylation by IL-6 and IL-10, but not by IFN-gamma, in primary macrophages. Inhibition of Stat activation correlated with inhibition of expression of IL-6-inducible genes. The inhibition was rapid and independent of de novo gene induction and occurred when the expression of suppressor of cytokine synthesis-3 was blocked. Inhibition of IL-6 signaling was mediated by the p38 subfamily of stress-activated protein kinases. Jak1 was inhibited at the level of tyrosine phosphorylation, indicating that inhibition occurred at least in part upstream of Stats in the Jak-Stat pathway. Experiments using Stat3 mutated at serine 727 and using truncated IL-6Rs suggested that the target of inhibition is contained within the membrane-proximal region of the cytoplasmic domain of the gp130 subunit of the IL-6 receptor and is different from the SH2 domain-containing protein-tyrosine phosphatase/suppressor of cytokine synthesis-3 docking site. These results identify a new level at which IL-1 and TNF-alpha modulate signaling by pleiotropic cytokines such as IL-6 and IL-10 and provide a molecular basis for the previously described antagonism of certain IL-6 actions by IL-1.     

First International Workshop on Porcine Chromosome 6

Recent advances in the use of microsatellite markers and the development of comparative gene mapping techniques have made the construction of high resolution genetic maps of livestock species possible. Framework and comprehensive genetic linkage maps of porcine chromosome 6 have resulted from the first international effort to integrate genetic maps from multiple laboratories. Eleven highly polymorphic genetic markers were exchanged and mapped by four independent laboratories on a total of 583 animals derived from four reference populations. The chromosome 6 framework map consists of 10 markers ordered with high local support. The average marker interval of the framework map is 15.1 cM (sex averaged). The framework map is 135, 175 and 109 cM in length (for sex averaged, female and male maps, respectively). The comprehensive map includes a total of 48 type I and type II markers with a sex averaged interval of 3.5 cM and is 166, 196 and 126 cM (for sex averaged, female and male maps, respectively). Additional markers within framework map marker intervals can thus be selected from the comprehensive map for further analysis of quantitive trait loci (QTL) located on chromosome 6. The resulting maps of swine chromosome 6 provide a valuable tool for analysing and locating QTL.     

Spectrophotometric methods for monitoring the microbial transformation of steroids. II. Absorbance ratio spectrophotometric determination of per cent conversion of 9 -fluoro-16 -hydroxyhydrocortisone to 9 -fluoro-16 -hydroxyprednisolone

A process method has been developed for estimating rapidly the conversion of 9α-fluoro-16α-hydroxyhydrocortisone to 9α-fluoro-16α-hydroxyprednisolone in fermentation broths. This allows frequent analyses of samples during the fermentation cycle. The absorbance ratio determination of conversion of the steroids is based on the measurement of the absorbance of aqueous steroid borate complexes at 241.5 mμ and 271 mμ.