From stowaways to karst‐aways: unloading the Peninsular Malaysia endemic Polyalthia brunneifolia (Annonaceae)

Detailed examination of specimens collected from limestone outcrops in Peninsular Malaysia and previously included in Polyalthia brunneifolia shows that they do not belong in this species. Three new species are described to accommodate these collections: Polyalthia chinii I.M.Turner & Utteridge from Bukit Serdam, Raub, Pahang; P. guabatuensis I.M.Turner & Utteridge from Batu Caves, Selangor, and P. guamusangensis I.M.Turner & Utteridge from Gua Musang, Kelantan. Conservation assessments are included for the new species and the general threats faced by species confined to limestone hills are discussed. In addition, an updated key to all species of Polyalthia known from Peninsular Malaysia is provided.     

小麦干尖叶的遗传研究初报

小麦干尖叶是近年在小麦育种中所发现的一种叶部坏死性状,直接影响小麦的产量。本文以具有干尖叶与正常叶这一相对性状的部分小麦品种(系)为基本材料,采用正反杂交、正反回交及杂种后代分析和异源细胞质替换,首次对干尖叶的遗传及性状传递规律进行了研究。结果表明:干尖叶性状与一般杂种坏死与黄化截然不同, 并非仅杂种所具有,能作为纯系稳定遗传; 其表型受核内一对主效显性基因所控制,即使采用异源细胞质替换, 以特定质核互作也难以克服这一性状的对外表达,只有通过杂交与后代选择,纯化与稳定隐性正常叶方可克服。 Abstract:In this paper,the inheritance and transmission law of the character for wheat leaf-tip necrosis were firstly investigated with the contrasting character of leaf-tip necrosis and normal leaf in wheat varieties for basic test materials by reciprocal crosses and backcrosses,hybrid progeny analysis and aliencytoplasm substitution.The results indicated that the wheat leaf-tip necrosis is abviously different from the hybrid necrosis and hybrid chlorosis.It is not only expressed in hybrid but also stable inheritance as pureline.Its phenotype is conditioned by a pair major dominant gene.It is not overcome even if special interaction of nucleus-cytoplasm after alien cytoplasm substitution.Only be the varieties or lines with normal leaf obtained by crossing and selecting stable normal leaf character with recessive gene.     

Evidence that up-regulation of the parotid Na+-K+-2Cl- cotransporter by hypertonic shrinkage is not duplicated by isotonic shrinkage

The application of Ca2+ mobilizing secretagogues to rat parotid acini results in a significant decrease in cell volume (15-30%) due to isotonic salt loss. It is often assumed that the effects of such an isotonic volume decrease can be mimicked by anisotonic cell shrinkage. We demonstrate that the Na+-K+-2Cl- cotransporter in these cells is up-regulated by Ca2+ mobilizing secretagogues as well as by cell shrinkage in hypertonic media. However, we find that although the protein kinase inhibitors staurosporine (0.3 M) and K252a (0.6 M) significantly blunt the latter up-regulation, they are without effect on the former. These observations suggest that hypertonic and isotonic shrinkage do not result in the activation of the same intracellular signalling pathways, and indicate that anisotonic volume perturbations may not provide good experimental models of physiologic isotonic volume changes.     

The Endothelin System and Endothelin-Converting Enzyme in the Brain: Molecular and Cellular Studies

The biologically active vasoactive peptides, the endothelins (ETs), are generated from inactive intermediates, the big endothelins, by a unique processing event catalysed by the zinc metalloprotease, endothelin converting enzyme (ECE). In this overview we examine the actions of endothelins in the brain, and focus on the structure and cellular locations of ECE. The heterogeneous distribution in the brain of ET-1, ET-2, and ET-3 is discussed in relation to their hemodynamic, mitogenic and proliferative properties as well as their possible roles as neurotransmitters. The cellular and subcellular localization of ECE in neuronal and in glial cells is compared with that of other brain membrane metalloproteases, neutral endopeptidase-24.11 (neprilysin), angiotensin converting enzyme and aminopeptidase N, which all function in neuropeptide processing and metabolism. Unlike these ectoenzymes, ECE exhibits a dual localisation in the cell, being present on the plasma membrane and also, in some instances, being concentrated in a perinuclear region. This differential localization may reflect distinct targeting of different ECE isoforms, ECE-l, ECE-1, and ECE-2.     

Cell-density-dependent sensitivity of a mer-lux bioassay.

The sensitivity of a previously described assay (O. Selifonova, R. Burlage, and T. Barkay, Appl. Environ. Microbiol. 59:3083-3090, 1993) for the detection of bioavailable inorganic mercury (Hg2+) by the activation of a mer-lux fusion was increased from nanomolar to picomolar concentrations by reducing biomass in the assays from 10(7) to 10(5) cells ml-1. The increase in sensitivity was due to a reduction in the number of cellular binding sites that may compete with the regulatory protein, MerR, for binding of the inducer, Hg2+. These results show that (i) the sensitivity of the mer-lux assay is sufficient for the detection of Hg2+ in most contaminated natural waters and (ii) mer-specified reactions, Hg2+ reduction and methylmercury degradation, can be induced in natural waters and may participate in the geochemical cycling of mercury.     

Collapsed xylem phenotype of Arabidopsis identifies mutants deficient in cellulose deposition in the secondary cell wall.

Recessive mutations at three loci cause the collapse of mature xylem cells in inflorescence stems of Arabidopsis. These irregular xylem (irx) mutations were identified by screening plants from a mutagenized population by microscopic examination of stem sections. The xylem cell defect was associated with an up to eightfold reduction in the total amount of cellulose in mature inflorescence stems. The amounts of cell wall-associated phenolics and polysaccharides were unaffected by the mutations. Examination of the cell walls by using electron microscopy demonstrated that the decreases in cellulose content of irx lines resulted in an alteration of the spatial organization of cell wall material. This suggests that a normal pattern of cellulose deposition may be required for assembly of lignin or polysaccharides. The reduced cellulose content of the stems also resulted in a decrease in stiffness of the stem material. This is consistent with the irregular xylem phenotype and suggests that the walls of irx plants are not resistant to compressive forces. Because lignin was implicated previously as a major factor in resistance to compressive forces, these results suggest either that cellulose has a direct role in providing resistance to compressive forces or that it is required for the development of normal lignin structure. The irx plants had a slight reduction in growth rate and stature but were otherwise normal in appearance. The mutations should be useful in facilitating the identification of factors that control the synthesis and deposition of cellulose and other cell wall components.     

Expression of a Cs(+)-resistant guard cell K+ channel confers Cs(+)-resistant, light-induced stomatal opening in transgenic arabidopsis.

Inward-rectifying K+ (K+in) channels in the guard cell plasma membrane have been suggested to function as a major pathway for K+ influx into guard cells during stomatal opening. When K+in channels were blocked with external Cs+ in wild-type Arabidopsis guard cells, light-induced stomatal opening was reduced. Transgenic Arabidopsis plants were generated that expressed a mutant of the guard cell K+in channel, KAT1, which shows enhanced resistance to the Cs+ block. Stomata in these transgenic lines opened in the presence of external Cs+. Patch-clamp experiments with transgenic guard cells showed that inward K+(in) currents were blocked less by Cs+ than were K+ currents in controls. These data provide direct evidence that KAT1 functions as a plasma membrane K+ channel in vivo and that K+in channels constitute an important mechanism for light-induced stomatal opening. In addition, biophysical properties of K+in channels in guard cells indicate that components in addition to KAT1 may contribute to the formation of K+in channels in vivo.     

rhGM—CSF／LIF融合蛋白基因的克隆及表达

利用基因重组技术,人工构建了一个编码五肽Ｇ－Ｓ－Ｇ－Ｇ－Ｓ的基因接头,将ＧＭ－ＣＳＦ和ＬＩＦ的ｃＤＮＡ相连而构成融合基因,将融合基因载入原核表达载体ｐＢＶ２２０后转化大肠杆菌,经热诱导后进行Ｗｅｓｔｅｒｎ印迹反应鉴定证实获得ｒｈＧＭ－ＣＳＦ／ＬＩＦ融合蛋白（简称ｒｈｇＭ－ＬＩＦ）活性测定表明重组的融合蛋白具有两因子双重活性。     

Available Light: Anthropological Reflections on Philosophical Topics

Available Light: Anthropological Reflections on Philosophical Topics. Clifford Geertz. Princeton: Princeton University Press, 2000. 27 lpp.