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Growth Sites (growth + site)
Selected AbstractsCandida albicans ABG1 gene is involved in endocytosisFEMS YEAST RESEARCH, Issue 2 2009Verónica Veses Abstract The human fungal pathogen Candida albicans undergoes reversible morphogenetic transitions between yeast, hyphal and pseudohyphal forms. The fungal vacuole actively participates in differentiation processes and plays a key role supporting hyphal growth. The ABG1 gene of C. albicans encodes an essential protein located in the vacuolar membranes of both yeast and hyphae. Using fluorescence microscopy of a green fluorescent protein-tagged version of Abg1p, a fraction of the protein was detected in hyphal tips, not associated with vacuolar membranes. Live cell imaging of emerging germ tubes showed that Abg1p migrated to the polarized growth site and colocalized with endocytic vesicles. Phenotypic analysis of a methionine-regulated conditional mutant confirmed that Abg1p is involved in endocytosis. [source] Methane efflux in relation to plant biomass and sediment characteristics in stands of three common emergent macrophytes in boreal mesoeutrophic lakesGLOBAL CHANGE BIOLOGY, Issue 1 2005Paula Kankaala Abstract Methane efflux was studied in stands of three emergent macrophyte species (Equisetum fluviatile, Schoenoplectus lacustris and Phragmites australis) commonly found in the littoral zone of boreal lakes. In vegetation stands with relatively low methane (CH4) emissions (<0.3 mol m,2 (ice-free period),1), the seasonal variation of CH4 efflux was better correlated with the dynamics of plant growth than variation in sediment temperature. In dense and productive vegetation stands that released high amounts of CH4 (2.3,7.7 mol m,2 (ice-free period),1), the seasonal variation in CH4 efflux was correlated with sediment temperature, indicating that methanogens were more limited by temperature than substrate supply. The bottom type at the growth site of the emergent plants significantly influenced the ratio of CH4 efflux to aboveground biomass of plants (Eff : B). The lowest Eff : B ratio was found in E. fluviatile stands growing on sand bottom under experimental conditions and the highest in P. australis -dominated littoral areas accumulating detritus from external sources. The future changes expected in the hydrology of boreal lakes and rivers because of climatic warming may impact the growth conditions of aquatic macrophytes as well as decomposition and accumulation of detritus and, thus, CH4 effluxes from boreal lakes. [source] Tri(propylene glycol) glycerolate diacrylate cross-linked polystyrene: a new resin support for solid-phase peptide synthesisCHEMICAL BIOLOGY & DRUG DESIGN, Issue 1 2003P.G. Sasikumar Abstract: A highly flexible, mechanically and chemically stable copolymer, tri(propylene glycol) glycerolate diacrylate cross-linked polystyrene (PS-TRPGGDA), was synthesized by the suspension polymerization and employed as a solid support for peptide synthesis. The beaded polymer support containing secondary hydroxyl functional groups in the cross-linker was used as the growth site for peptide synthesis. The procedure is unique and cost-effective in that it avoids the initial functionalization steps required for most of the styrene-based polymer supports. The resin was characterized by 13C-CP-MAS NMR spectroscopy and the morphologic features of the resin were investigated using scanning electron microscopy. Swelling studies conducted on the new support revealed that the PS-TRPGGDA resin undergoes more effective swelling and solvation than PS-DVB resin in all solvents used in peptide synthesis. The efficiency of the new support was demonstrated by synthesizing a ,difficult' sequence Ala-Arg-(Ala)6 -Lys and comparing it with commercially available Merrifield and Sheppard resins. The synthetic efficiency was further demonstrated by the synthesis of a 24-residue NR 2A peptide substrate of calcium/calmodulin-binding peptide. The high yield and purity of the peptide synthesized on the novel support indicates the positive role of the flexible and hydrophilic cross-linking agent in the solid support. [source] Effect of differences in cancer cells and tumor growth sites on recruiting bone marrow-derived endothelial cells and myofibroblasts in cancer-induced stromaINTERNATIONAL JOURNAL OF CANCER, Issue 6 2005Takafumi Sangai Abstract Cancer-stromal interaction is well known to play important roles during cancer progression. Recently we have demonstrated that bone marrow-derived vascular endothelial cells (BMD-VE) and myofibroblasts (BMD-MF) are recruited into the human pancreatic cancer cell line Capan-1 induced stroma. To assess the effect of the difference in cancer cell types on the recruitment of BMD-VE and BMD-MF, 10 kinds of human cancer cell line were implanted into the subctaneous tissue of the immunodeficient mice transplanted with bone marrow of double-mutant mice (RAG-1,/, ,-gal Tg or RAG-1,/, GFP Tg). The recruitment frequency of BMD-VE (%BMD-VE) and BMD-MF (%BMD-MF), and tumor-associated parameters [tumor volume (TV), microvessel density (MVD) and stromal proportion (%St)] were measured. The correlation among them was analyzed. Although %BMD-VE and %BMD-MF varied (from 0 to 21.6%, 0 to 29.6%, respectively), depending on the cancer cell line, both parameters were significantly correlated with %St (p < 0.005). Furthermore %BMD-VE and %BMD-MF also significantly correlated (p < 0.005). In order to assess the effect of tumor growth sites on the recruitment of the cells of interest, a human pancreatic cancer cell line, Capan-1, was transplanted into 5 different sites: subcutaneous tissue, peritoneum, liver, spleen and lung. Tumors in the subcutaneous tissue and peritoneum induced desmoplastic stroma (%St = 22.7%, 19.5%, respectively) and contained BMD-VE (%BMD-VE = 21.6%, 16.5% respectively) and BMD-MF (%BMD-MF = 29.6%, 24.5%, respectively), but weak stromal induction without recruitment of BMD-VE or -MF was observed in the tumors at of the liver, spleen and lung (%St = 9.7%, 9.1%, 5.4%, respectively). cDNA microarray analysis identified the 29 genes that expression was especially up- or down-regulated in the cell line that induced an abundant stromal reaction. However they did not encoded the molecules that were directly involved in stromal cell recruitment (chemokines), differentiation (cytokines) or proliferation (growth factors). These results indicate that the recruitment of BMD-VE and -MF is required for stromal formation during cancer progression and that the cancer microenvironment is important in stromal reaction and the recruitment of BMD-VE and -MF. © 2005 Wiley-Liss, Inc. [source] Nutrient requirements of ephemeral plant species from wet, mesotrophic soilsJOURNAL OF VEGETATION SCIENCE, Issue 3 2001Emiel; Brouwer van der Meijden (1996) Abstract. Nanocyperion plant communities occur on wet, more or less nutrient-poor and sparsely vegetated soils in temperate climates and are characterized by tiny, very shortlived plant species. Most of these have become locally extinct. It is generally assumed that drainage and eutrophication were the most important reasons for this decrease. However, chemical analysis of soil pore water from plots on growth sites of these ephemerals showed that phosphorus availability was relatively high. In a greenhouse experiment, the growth of ephemeral species was strongly limited by the amount of available phosphorus, whereas there was little or no limitation to the growth of other plant species from this habitat. At low phosphorus concentrations, the ephemeral species reached their reproductive phase within the same period, but showed a strong reduction in the amount of flowers that were produced. We concluded that ephemeral species in particular require a minimum amount of phosphorus for reproduction. Other species on nutrient-poor, wet soils have a longer life span and can postpone flowering in nutrient-poor soils. In contrast to other short-lived plant species from the same habitat, the growth of ephemeral species was barely stimulated by enhanced nitrogen availability. Apparently, the ephemerals are adapted to low nitrogen concentrations. The occurrence on nitrogen-poor and relatively phosphorus-rich soils suggests that this community may be very sensitive to nitrogen deposition. Reduced phosphorus availability below the minimum requirements of ephemerals, for example after acidification or the exclusion of human activities, has possibly contributed to the decrease of ephemeral plant species. [source] High drive current and high frequency response of GaN nanowire metal-oxide-semiconductor field-effect transistorPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 7-8 2010Jeng-Wei Yu Abstract We report the techniques of lateral epitaxial growth of horizontally aligned [110] GaN NWs and the photo-enhanced chemical (PEC) oxidation process to enable the registration of crystalline gallium oxide (Ga2O3)/GaN NWs onto their growth sites over the SiO2/p-Si substrates. This method allows the implementation of top-gate Ga2O3/GaN NW-metal oxide semiconductor field effect transistor (MOSFET) using the conventional optical lithography and the metal lift-off procedures. This scheme enables photolithographic fabrication of top-gate Ga2O3/GaN NW-MOSFET of 60 nm dia. and 2 ,m gate length. Device parameters with gm of 40 ,S, saturation current of 90 ,A, and cut-off frequency fT at 22 GHz have been extracted (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Adjustment of leaf photosynthesis to shade in a natural canopy: rate parametersPLANT CELL & ENVIRONMENT, Issue 3 2005A. LAISK ABSTRACT The present study was performed to investigate the adjustment of the rate parameters of the light and dark reactions of photosynthesis to the natural growth light in leaves of an overstorey species, Betula pendula Roth, a subcanopy species, Tilia cordata P. Mill., and a herb, Solidago virgaurea L., growing in a natural plant community in Järvselja, Estonia. Shoots were collected from the site and individual leaves were measured in a laboratory applying a standardized routine of kinetic gas exchange, Chl fluorescence and 820 nm transmittance measurements. These measurements enabled the calculations of the quantum yield of photosynthesis and rate constants of excitation capture by photochemical and non-photochemical quenchers, rate constant for P700+ reduction via the cytochrome b6f complex with and without photosynthetic control, actual maximum and potential (uncoupled) electron transport rate, stomatal and mesophyll resistances for CO2 transport, Km(CO2) and Vm of ribulose-bisphosphate carboxylase-oxygenase (Rubisco) in vivo. In parallel, N, Chl and Rubisco contents were measured from the same leaves. No adjustment toward higher quantum yield in shade compared with sun leaves was observed, although relatively more N was partitioned to the light-harvesting machinery in shade leaves (H. Eichelmann et al., 2004). The electron transport rate through the Cyt b6f complex was strongly down-regulated under saturating light compared with darkness, and this was observed under atmospheric, as well as saturating CO2 concentration. In vivo Vm measurements of Rubisco were lower than corresponding reported measurements in vitro, and the kcat per reaction site varied widely between leaves and growth sites. The correlation between Rubisco Vm and the photosystem I density was stronger than between Vm and the density of Rubisco active sites. The results showed that the capacity of the photosynthetic machinery decreases in shade-adjusted leaves, but it still remains in excess of the actual photosynthetic rate. The photosynthetic control systems that are targeted to adjust the photosynthetic rate to meet the plant's needs and to balance the partial reactions of photosynthesis, down-regulate partial processes of photosynthesis: excess harvested light is quenched non-photochemically; excess electron transport capacity of Cyt b6f is down-regulated by ,pH-dependent photosynthetic control; Rubisco is synthesized in excess, and the number of activated Rubisco molecules is controlled by photosystem I-related processes. Consequently, the nitrogen contained in the components of the photosynthetic machinery is not used at full efficiency. The strong correlation between leaf nitrogen and photosynthetic performance is not due to the nitrogen requirements of the photosynthetic apparatus, but because a certain amount of energy must be captured through photosynthesis to maintain this nitrogen within a leaf. [source] | ||||||||||