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Decreasing Concentration (decreasing + concentration)
Selected AbstractsAre nutrient availability and acidity-alkalinity gradients related in Sphagnum-dominated peatlands?JOURNAL OF VEGETATION SCIENCE, Issue 4 2002L. Bragazza Pignatti (1982) for vascular plants; Frahm & Frey (1987) for bryophytes Abstract. Gradients in acidity-alkalinity and nutrient availability were studied in 2 Sphagnum -dominated peatlands on the southeastern Italian Alps. Decreasing concentrations of most mineral elements (Ca2+, Mg2+, Mn2+, Al3+ and Si4+) in pore water indicated a progressively lower influx of mineral-soil water from the slightly minerotrophic conditions in the peatland margins to ombrogenous conditions in the central part of the peatlands. This was paralleled by decreasing concentrations of ash, bulk density, Ca, Fe and, partly, Mn in the peat. The nutrient gradient, as defined by pore water concentrations of N and P, was largely independent of the acidity- alkalinity gradient: NO3- and PO43- had similar concentrations throughout the gradient, whereas NH4+ concentrations increased with increasing pore-water pH. In contrast, the peat nutrient gradient coincided with the acidity-alkalinity gradient, with total concentrations of N and P decreasing from the margin to the centre. Bryophytes and vascular plants had different responses along the acidity-alkalinity gradient and the nutrient gradient. Bryophyte distribution reflected the acidity-alkalinity gradient both in pore water and in peat. Vascular plant distribution was mainly influenced by variations in nutrient availability. [source] On the relationship between methane production and oxidation by anaerobic methanotrophic communities from cold seeps of the Gulf of MexicoENVIRONMENTAL MICROBIOLOGY, Issue 5 2008Beth! Orcutt Summary The anaerobic oxidation of methane (AOM) in the marine subsurface is a significant sink for methane in the environment, yet our understanding of its regulation and dynamics is still incomplete. Relatively few groups of microorganisms consume methane in subsurface environments , namely the anaerobic methanotrophic archaea (ANME clades 1, 2 and 3), which are phylogenetically related to methanogenic archaea. Anaerobic oxidation of methane presumably proceeds via a ,reversed' methanogenic pathway. The ANME are generally associated with sulfate-reducing bacteria (SRB) and sulfate is the only documented final electron acceptor for AOM in marine sediments. Our comparative study explored the coupling of AOM with sulfate reduction (SR) and methane generation (MOG) in microbial communities from Gulf of Mexico cold seep sediments that were naturally enriched with methane and other hydrocarbons. These sediments harbour a variety of ANME clades and SRB. Following enrichment under an atmosphere of methane, AOM fuelled 50,100% of SR, even in sediment slurries containing petroleum-associated hydrocarbons and organic matter. In the presence of methane and sulfate, the investigated microbial communities produce methane at a small fraction (,10%) of the AOM rate. Anaerobic oxidation of methane, MOG and SR rates decreased significantly with decreasing concentration of methane, and in the presence of the SR inhibitor molybdate, but reacted differently to the MOG inhibitor 2-bromoethanesulfonate (BES). The addition of acetate, a possible breakdown product of petroleum in situ and a potential intermediate in AOM/SR syntrophy, did not suppress AOM activity; rather acetate stimulated microbial activity in oily sediment slurries. [source] Impact of damming the Mogi-Guaçu River (São Paulo State, Brazil) on reservoir limnological variablesLAKES & RESERVOIRS: RESEARCH AND MANAGEMENT, Issue 1 2008Ana Lúcia Brandimarte Abstract This study examined the effects of the damming of the Mogi-Guaçu River (São Paulo State, Brazil) on the surface current velocity, water temperature, Secchi disc transparency, turbidity, colour, conductivity, pH and concentrations of nutrients and pigments. Surface-water samples were taken before, during and after the reservoir was filled. Three sampling sites were established, one in the upper reach of the reservoir, one in the central area of the reservoir and one downstream from the dam. An additional sampling site was established on the Peixe River, the major tributary of the Mogi-Guaçu in the study area. After filling of the reservoir, the surface current velocity tended to decrease, excepting downstream of the dam. The pH, and the Kjeldahl nitrogen, ammonia and chlorophyll- a concentrations, tended to increase. The nitrite concentrations increased mainly in the upper reach and central area of the reservoir. The Secchi disc transparency and colour tended to decrease. A decreasing trend in dissolved oxygen concentration was observed mainly at the central area of reservoir. The conductivity tended to decrease, later returning to levels observed prior to reservoir filling. The nitrate, total phosphorus and orthophosphate concentrations exhibited an increasing trend after reservoir filling, followed by a decreasing concentration, reaching lower levels than those found prior to reservoir filling. High phaeophytin concentrations were measured for the filling phase. The observed water quality changes for Mogi-Guaçu Reservoir generally were not as extreme as those observed for other tropical reservoirs. This trend was related to the operation of the reservoir. As Mogi-Guaçu Reservoir is a run-of-the-river reservoir with a short water retention time, the flooded area is not extensive and the retention of material and sedimentation upstream from the dam is not remarkable. These facts explain the small water quality changes observed for most of the variables after reservoir filling. The water quality decreased at the in-lake site in the central part of the reservoir, attaining a hypereutrophic condition. This fact was related to the ageing of the reservoir and to cultural eutrophication. [source] Phenolic compounds in peach (Prunus persica) cultivars at harvest and during fruit maturationANNALS OF APPLIED BIOLOGY, Issue 1 2008C. Andreotti Abstract Six peach and six nectarine cultivars were evaluated for the phenolic content in their pulp and peel tissues. Chlorogenic acid, catechin, epicatechin, rutin and cyanidin-3-glucoside were detected as the main phenolic compounds of ripened fruits. The concentration was always higher in peel tissue, with average values ranging from 1 to 8 mg g,1 dry weight (DW) depending on cultivar. Of the tested varieties, the white-flesh nectarine ,Silver Rome' emerged as the cultivar with the highest amount of total phenolics. Phenolic compounds were also profiled during fruit growth and ripening in the yellow nectarine cv. ,Stark Red Gold', which showed a decreasing concentration during fruit development in both peel and pulp tissues. Average amounts of total phenolics were approximately 25 mg g,1 DW 60 days after full bloom and decreased to 3 mg g,1 DW at ripening in pulp tissue. Differences among peel and pulp composition show the different dietetic and antioxidant potential of fruits consumed unpeeled and peeled. [source] Reduced apoptosis in BALB/c mice infected with Heligmosomoides polygyrusPARASITE IMMUNOLOGY, Issue 6 2007M. DOLIGALSKA SUMMARY We evaluated levels of apoptosis and the immune response ex vivo in BALB/c mice infected with Heligmosomoides polygyrus. Cell proliferation, apoptosis and cytokine production were measured in mesenteric lymph nodes (MLN) without exposure to H. polygyrus antigens in culture. The inhibited apoptosis and cytokine production reported might reflect a state of cell hyporesponsiveness in the prepatent phase of infection. These changes were accompanied by changes in the percentage of CD4+ cells in MLN and popliteal lymph nodes (PLN). The prolonged reduction in apoptosis coexisted with induced cell proliferation, elevated TNF-,, IL-12p70, IFN-,, IL-6, IL-10 and TGF-, synthesis, but lowered IL-4 and IL-2 levels. In the chronic phase of infection an increasing production of IFN-,, monocyte chemotactic protein-1 (MCP-1), IL-10 and TGF-, with decreasing concentrations of other cytokines resulted in restored apoptosis. The cytokine response in serum showed moderate production of TNF-,, temporary involvement of IL-12p70, induction of IFN-, and IL-10 synthesis, as well as growing IL-6 and MCP-1 production. It is suggested that a synchronized synthesis of distinct cytokines is accompanied by different levels of inhibited apoptosis during the prepatent and chronic phases of H. polygyrus infection in BALB/c mice. We suggest that immunosuppression provoked by the nematode is not the outcome of parasite-induced apoptosis, but rather results from a hyporesponsiveness experienced by cells during H. polygyrus infection. [source] | |||||||||||||