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Potential Activity (potential + activity)
Selected AbstractsSeasonal variation in enzyme activities and temperature sensitivities in Arctic tundra soilsGLOBAL CHANGE BIOLOGY, Issue 7 2009MATTHEW D. WALLENSTEIN Abstract Arctic soils contain large amounts of organic matter due to very slow rates of detritus decomposition. The first step in decomposition results from the activity of extracellular enzymes produced by soil microbes. We hypothesized that potential enzyme activities are low relative to the large stocks of organic matter in Arctic tundra soils, and that enzyme activity is low at in situ temperatures. We measured the potential activity of six hydrolytic enzymes at 4 and 20 °C on four sampling dates in tussock, intertussock, shrub organic, and shrub mineral soils at Toolik Lake, Alaska. Potential activities of N -acetyl glucosaminidase, ,-glucosidase, and peptidase tended to be greatest at the end of winter, suggesting that microbes produced enzymes while soils were frozen. In general, enzyme activities did not increase during the Arctic summer, suggesting that enzyme production is N-limited during the period when temperatures would otherwise drive higher enzyme activity in situ. We also detected seasonal variations in the temperature sensitivity (Q10) of soil enzymes. In general, soil enzyme pools were more sensitive to temperature at the end of the winter than during the summer. We modeled potential in situ,-glucosidase activities for tussock and shrub organic soils based on measured enzyme activities, temperature sensitivities, and daily soil temperature data. Modeled in situ enzyme activity in tussock soils increased briefly during the spring, then declined through the summer. In shrub soils, modeled enzyme activities increased through the spring thaw into early August, and then declined through the late summer and into winter. Overall, temperature is the strongest factor driving low in situ enzyme activities in the Arctic. However, enzyme activity was low during the summer, possibly due to N-limitation of enzyme production, which would constrain enzyme activity during the brief period when temperatures would otherwise drive higher rates of decomposition. [source] Localization of processes involved in methanogenic degradation of rice straw in anoxic paddy soilENVIRONMENTAL MICROBIOLOGY, Issue 8 2001Kristin Glissmann In anoxic paddy soil, rice straw is decomposed to CH4 and CO2 by a complex microbial community consisting of hydrolytic, fermenting, syntrophic and methanogenic microorganisms. Here, we investigated which of these microbial groups colonized the rice straw and which were localized in the soil. After incubation of rice straw in anoxic soil slurries for different periods, the straw pieces were removed from the soil, and both slurry and straw were studied separately. Although the potential activities of polysaccharolytic enzymes were higher in the soil slurry than in the straw incubations, the actual release of reducing sugars was higher in the straw incubations. The concentrations of fermentation products, mainly acetate and propionate, increased steadily in the straw incubations, whereas only a little CH4 was formed. In the soil slurries, on the other hand, fermentation products were low, whereas CH4 production was more pronounced. The production of CH4 or of fermentation products in the separated straw and soil incubations accounted in sum for 54,82% of the CH4 formed when straw was not removed from the soil. Syntrophic propionate degradation to acetate, CO2 and H2 was thermodynamically more favourable in the soil than in the straw fraction. These results show that hydrolysis and primary fermentation reactions were mainly localized on the straw pieces, whereas the syntrophic and methanogenic reactions were mainly localized in the soil. The percentage of bacterial relative to total microbial 16S rRNA content was higher on the straw than in the soil, whereas it was the opposite for the archaeal 16S rRNA content. It appears that rice straw is mainly colonized by hydrolytic and fermenting bacteria that release their fermentation products into the soil pore water where they are further degraded to CH4. Hence, complete methanogenic degradation of straw in rice soil seems to involve compartmentalization. [source] Creativity and Picture BooksLITERACY, Issue 2 2000Judith Graham Where authors and illustrators exercise rigorous constraint with their texts, with neither replicating the work that the other can portray more effectively, they are at their most creative and they make picture books to which readers are repeatedly drawn because of the inherent and deeply satisfying challenges offered. Moreover, the allure is not just to children; teachers find that such texts draw from them their most creative ideas for ways of working with children. Three picture books are examined in terms of their strengths and potential activities. Conclusions are drawn which seek to justify the sharing of such picture books in terms of imaginative empowerment and lasting messages about reading. [source] Seasonal variation in enzyme activities and temperature sensitivities in Arctic tundra soilsGLOBAL CHANGE BIOLOGY, Issue 7 2009MATTHEW D. WALLENSTEIN Abstract Arctic soils contain large amounts of organic matter due to very slow rates of detritus decomposition. The first step in decomposition results from the activity of extracellular enzymes produced by soil microbes. We hypothesized that potential enzyme activities are low relative to the large stocks of organic matter in Arctic tundra soils, and that enzyme activity is low at in situ temperatures. We measured the potential activity of six hydrolytic enzymes at 4 and 20 °C on four sampling dates in tussock, intertussock, shrub organic, and shrub mineral soils at Toolik Lake, Alaska. Potential activities of N -acetyl glucosaminidase, ,-glucosidase, and peptidase tended to be greatest at the end of winter, suggesting that microbes produced enzymes while soils were frozen. In general, enzyme activities did not increase during the Arctic summer, suggesting that enzyme production is N-limited during the period when temperatures would otherwise drive higher enzyme activity in situ. We also detected seasonal variations in the temperature sensitivity (Q10) of soil enzymes. In general, soil enzyme pools were more sensitive to temperature at the end of the winter than during the summer. We modeled potential in situ,-glucosidase activities for tussock and shrub organic soils based on measured enzyme activities, temperature sensitivities, and daily soil temperature data. Modeled in situ enzyme activity in tussock soils increased briefly during the spring, then declined through the summer. In shrub soils, modeled enzyme activities increased through the spring thaw into early August, and then declined through the late summer and into winter. Overall, temperature is the strongest factor driving low in situ enzyme activities in the Arctic. However, enzyme activity was low during the summer, possibly due to N-limitation of enzyme production, which would constrain enzyme activity during the brief period when temperatures would otherwise drive higher rates of decomposition. [source] Emamectin, a novel insecticide for controlling field crop pests,PEST MANAGEMENT SCIENCE (FORMERLY: PESTICIDE SCIENCE), Issue 11 2002Isaac Ishaaya Abstract Emamectin is a macrocyclic lactone insecticide with low toxicity to non-target organisms and the environment, and is considered an important component in pest-management programmes for controlling field crop pests. It is a powerful compound for controlling the cotton bollworm Helicoverpa armigera (Hübner). A spray concentration of 25,mg AI litre,1 in a cotton field resulted in over 90% suppression of H armigera larvae up to day 28 after treatment, while similar mortality of the Egyptian cotton leafworm Spodoptera littoralis Boisduval, under the same conditions, was maintained for 3 days only. Emamectin is a potent compound for controlling the western flower thrips Frankliniella occidentalis (Pergande) under both laboratory and field conditions and its activity on adults was over 10-fold greater than that of abamectin. Spray concentrations of 10 and 50,mg AI litre,1 in Ageratum houstonianum Mill flowers resulted in total suppression of adults up to day 11 and of larvae up to day 20 after treatment. Under standard laboratory conditions, emamectin exhibits a considerable activity on the whitefly Bemisia tabaci (Gennadius) and the leafminer Liriomyza huidobrensis (Blanchard). Further studies are required to evaluate its potential activity on the latter pests under field conditions. © 2002 Society of Chemical Industry [source] Identification of taxanes in extracts from leaves of Taxus baccata L. using 13C-NMR spectroscopyPHYTOCHEMICAL ANALYSIS, Issue 3 2009Emilie Duquesnoy Abstract Introduction The study of taxanes is a hot topic worldwide because of their potential activity against cancer. Analysis of taxanes in extracts of various Taxus species is generally achieved using HPLC. Objective The aim of the current work was to identify taxanes in different fractions of extracts from Taxus baccata L. using the computer-aided analysis of their 13C-NMR spectra. Methodology A computerised procedure, based on 13C-NMR spectroscopy using literature data, has been developed in order to identify taxoids in natural mixtures. Leaves and twigs of T. baccata were extracted with various solvents and the extracts were fractionated according to rapid fractionation schemes described in the literature. Results The computer-assisted analysis of the 13C-NMR spectra of the fractions of chromatography led to the identification of 16 taxanes belonging to the taxine, taxicine, taxinine and taxuspine families. Conclusion It has been shown that 13C-NMR is a powerful alternative tool for the identification of taxanes in extracts of leaves and twigs of various Taxus species after a rapid fractionation step. Copyright © 2009 John Wiley & Sons, Ltd. [source] Treatment of rheumatoid arthritis with a syk kinase inhibitor: A twelve-week, randomized, placebo-controlled trial,ARTHRITIS & RHEUMATISM, Issue 11 2008Michael E. Weinblatt Objective Spleen tyrosine kinase (Syk) has been identified as an important modulator of immune signaling in B cells and cells bearing Fc,-activating receptors. R788, a prodrug of active metabolite R406, has been shown to be an inhibitor of Syk kinase, active in a variety of in vitro and in vivo models, suggesting potential activity in the treatment of rheumatoid arthritis (RA). Methods We enrolled 189 patients with active RA despite methotrexate therapy in a 3-month, multicenter, ascending-dose, double-blind, placebo-controlled trial. The primary end point was the American College of Rheumatology 20% improvement criteria (ACR20) response rate at week 12. Results Twice-daily oral doses of 100 mg and 150 mg of R788 were significantly superior to placebo or twice-daily oral doses of 50 mg at week 12 (ACR20 achieved in 65% and 72% versus 38% and 32% of patients, respectively [P < 0.01]). ACR50 (achieved in 49% and 57% versus 19% and 17% of patients, respectively) and ACR70 (achieved in 33% and 40% versus 4% and 2% of patients, respectively) scores showed a similar pattern. Clinical effect was noted as early as 1 week after initiation of therapy. Reductions in serum interleukin-6 and matrix metalloproteinase 3 levels also occurred as early as week 1 in the groups receiving 100 mg and 150 mg R788. The major adverse effects were gastrointestinal side effects (predominantly diarrhea) and neutropenia (<1,500/mm3), both of which were dose related. Conclusion These results indicate that an inhibitor of Syk kinase produces significant clinical benefits at 12 weeks in a population of patients with active RA receiving methotrexate therapy. Syk kinase may be an important new therapeutic target in RA and related autoimmune conditions. [source] In vitro biotransformation of imatinib by the tumor expressed CYP1A1 and CYP1B1BIOPHARMACEUTICS AND DRUG DISPOSITION, Issue 2 2008Bertrand Rochat Abstract The main objective of the study was to examine the biotransformation of the anticancer drug imatinib in target cells by incubating it with oxidoreductases expressed in tumor cells. The second objective was to obtain an in silico prediction of the potential activity of imatinib metabolites. An in vitro enzyme kinetic study was performed with cDNA expressed human oxidoreductases and LC-MS/MS analysis. The kinetic parameters (Km and Vmax) were determined for six metabolites. A molecular modeling approach was used to dock these metabolites to the target Abl or Bcr-Abl kinases. CYP3A4 isozyme showed the broadest metabolic capacity, whereas CYP1A1, CYP1B1 and FMO3 isozymes biotransformed imatinib with a high intrinsic clearance. The predicted binding modes for the metabolites to Abl were comparable to that of the parent drug, suggesting potential activity. These findings indicate that CYP1A1 and CYP1B1, which are known to be overexpressed in a wide range of tumors, are involved in the biotransformation of imatinib. They could play a role in imatinib disposition in the targeted stem, progenitor and differentiated cancer cells, with a possible contribution of the metabolites toward the activity of the drug. Copyright © 2008 John Wiley & Sons, Ltd. [source] | ||||||||||||||||