Bacterial and fungal response to nitrogen fertilization in three coniferous forest soils

Forest soil carbon (C) pools may act as sinks for, or sources of, atmospheric carbon dioxide, while nitrogen (N) fertilization may affect the net exchange of C in forest ecosystems. Since all major C and N processes in soil are driven by soil microorganisms, we evaluated the effects of N fertilization on biomass and bacterial and fungal activity in soils from three Norway spruce forests with different climatic and N availability conditions. N deposition and net N mineralization were higher at the sites in southern Sweden than at the site in northern Sweden. We also studied the extent to which N fertilization altered the nutrient(s) limiting bacterial growth in soil. We found that on average microbial biomass was reduced by ～40% and microbial activity by ～30% in fertilized plots. Bacterial growth rates were more negatively affected by fertilization than fungal growth rates, while fungal biomass (estimated using the phospholipid fatty acid (PLFA) 18:2ω6,9) decreased more than bacterial biomass as a consequence of fertilization. The microbial community structure (indicated by the PLFA pattern) was changed by fertilization, but not in the same way at the three sites. Soil bacteria were limited by a lack of carbon in all forests, with the carbon limitation becoming more evident in fertilized plots, especially in the forests that had previously been the most N-limited ones. This study thus showed that the effects of N fertilization differed depending on the conditions at the site prior to fertilization.     

Inhibition of cancer cell proliferation in vitro by fruit and berry extracts and correlations with antioxidant levels

The effects of 10 different extracts of fruits and berries on cell proliferation of colon cancer cells HT29 and breast cancer cells MCF-7 were investigated. The fruits and berries used were rosehips, blueberries, black currant, black chokeberries, apple, sea buckthorn, plum, lingonberries, cherries, and raspberries. The extracts decreased the proliferation of both colon cancer cells HT29 and breast cancer cells MCF-7, and the effect was concentration dependent. The inhibition effect for the highest concentration of the extracts varied 2-3-fold among the species, and it was in the ranges of 46-74% (average = 62%) for the HT29 cells and 24-68% (average = 52%) for the MCF-7 cells. There were great differences in the content of the analyzed antioxidants in the extracts. The level of the vitamin C content varied almost 100-fold, and the content of total carotenoids varied almost 150-fold among the species. Also in the composition and content of flavonols, hydroxycinnamic acids, anthocyanins, and phenolics were found great differences among the 10 species. The inhibition of cancer cell proliferation seen in these experiments correlated with levels of some carotenoids and with vitamin C levels, present at levels that can be found in human tissues. The same inhibition of cell proliferation could not be found by ascorbate standard alone. This correlation might indicate a synergistic effect of vitamin C and other substances. In MCF-7 cells, the anthocyanins may contribute to the inhibition of proliferation.     

The structure of the first coordination shell in liquid water

X-ray absorption spectroscopy and x-ray Raman scattering were used to probe the molecular arrangement in the first coordination shell of liquid water. The local structure is characterized by comparison with bulk and surface of ordinary hexagonal ice Ih and with calculated spectra. Most molecules in liquid water are in two hydrogen-bonded configurations with one strong donor and one strong acceptor hydrogen bond in contrast to the four hydrogen-bonded tetrahedral structure in ice. Upon heating from 25 degrees C to 90 degrees C, 5 to 10% of the molecules change from tetrahedral environments to two hydrogen-bonded configurations. Our findings are consistent with neutron and x-ray diffraction data, and combining the results sets a strong limit for possible local structure distributions in liquid water. Serious discrepancies with structures based on current molecular dynamics simulations are observed.     

Inhibition of cytotoxicity of lymphocytes by concanavalin A in vitro

Human lymphocytes treated with the plant protein concanavalin A are stimulated to transform into blasts, without developing cytotoxicity for chicken erythrocytes. Prior treatment of lymphocytes with concanavalin A potentiated phytohemagglutinin-induced blast transformation and DNA synthesis but completely inhibited phytohemagglutinin-induced cytotoxicity. Inhibiton was not due to suppression of the mixed lymphocyte-erythrocyte aggregation normally caused by phytohemagglutinin. Inhibition of cytotoxicity was reversible when concanavalin A was removed from the lymphocytes by treatment with methyl-alpha-D-manno-pyranoside after 1 hour but not after 20 hours. The results indicate that blast transformation and cytotoxicity are separate expressions of lymphocyte stimulation.     

Decreased levels of tobacco-specific N-nitrosamines in moist snuff on the Swedish market

Moist snuff, or snus, on the Swedish market in 2001 and 2002 was analyzed for tobacco-specific N-nitrosamines (TSNAs) using a recently developed LC-MS/MS method. All samples of moist snuff analyzed were found to contain detectable levels of N'-nitrosonornicotine (NNN), N'-nitrosoanatabine (NAT), N'-nitrosoanabasine (NAB), and 4-(N-methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK). In the survey in 2001, all samples except for one were produced by Swedish Match (n = 14), which is the dominating manufacturer on the Swedish snuff market. In the survey in 2002, samples from both Swedish Match (n = 7) and seven smaller manufacturers (n = 20) were analyzed. Total TSNA levels of between 0.15 and 3.0 microg/g wet weight were found. In the survey in 2001 and 2002, the mean level of the total TSNA content in moist snuff was 1.1 microg/g (n = 14) and 1.0 microg/g (n = 27), respectively. The result of the survey shows that the level of TSNAs in moist snuff on the Swedish market has been greatly reduced since the middle of the 1980s. Clearly, efforts have been made by the manufacturers to reduce the level of TSNAs in snuff.     

Spatial visualization of progressive states of maturing lentivirus.

Progressive states of maturing lentivirus: maedia visna virus (MVV) and human immunodeficiency virus (HIV), respectively, have been visualized by 2-D electron microscopy and by 3-D electron microscopic tomography. A major fraction of MVV and a low percentage of HIV appear as immature particles 4 to 5 days post virus infection. Upon budding the gag-precursor material is densely packed inside the external envelope. After virus release the major portion of precursors is assembled within an approximately 25 nm thick layer directly attached to the envelope. Structural maturation of the core is different for the two viruses. Pleomorphic cores are observed in mature MVV in contrast to structurally defined cores of HIV. The latter are principally cone-shaped, spanning the entire diameter of the virion with a 40 to 60 nm wide free end and an approximately 20 nm narrow end attached to the envelope with a core-envelope-link.     

Hydrology influences breeding time in the white-throated dipper

While nitrogen and carbon stable isotope values can reflect ecological segregation, prey choice and spatial distribution in seabirds, the interpretation of bulk stable isotope values is frequently hampered by a lack of isotopic baseline data. In this study, we used compound-specific isotope analyses of amino acids (CSIA-AA) to overcome this constraint and to study interspecific differences, seasonal and historical changes in trophic positions of five seabird species, three penguins and two petrels, from a sub-Antarctic seabird community. CSIA-AA allowed comparing trophic positions of seabirds with temperate and polar distributions. Gentoo and Magellanic penguins had the highest trophic positions during the breeding season (3.7 and 3.9), but decreased these (2.9 and 3.3) during the feed-up for moult. Intra-specific differences were also detected in Thin-billed prions, where carbon isotope values clearly separated individuals with polar and temperate distributions, both in the breeding and interbreeding periods. Thin-billed prions that foraged in polar waters had lower trophic positions (3.2) than conspecifics foraging in temperate waters (3.8). We further investigated historical changes by comparing museum samples with samples collected recently. Our pilot study suggests that Rockhopper penguins, Magellanic penguins and Thin-billed prions with temperate non-breeding distributions had retained their trophic levels over a 90–100 year period, while Gentoo penguins and Thin-billed prions with polar non-breeding distributions had decreased trophic levels compared to historical samples. In contrast, Wilson’s storm-petrels had slightly increased trophic levels compared to samples taken in 1924–1930. We applied compound-specific stable isotope analyses across a range of contexts, from intra-specific comparisons between stages of the breeding cycle to inter-specific seabird community analysis that would not have been possible using bulk stable isotope analyses alone due to differences in isotopic baselines.     

Fragmentation and flow regulation of the world's large river systems

A global overview of dam-based impacts on large river systems shows that over half (172 out of 292) are affected by dams, including the eight most biogeographically diverse. Dam-impacted catchments experience higher irrigation pressure and about 25 times more economic activity per unit of water than do unaffected catchments. In view of projected changes in climate and water resource use, these findings can be used to identify ecological risks associated with further impacts on large river systems.