Movement of N from decomposing earthworm tissue to soil microbial and plant N pools

Abstract A microcosm experiment was made to determine the fate of nitrogen released from 15 N-labelled decomposing earthworms (Lumbricus terrestris) in soil in the presence or absence of ryegrass seedlings (Lolium perenne). Earthworm tissue (2.0% 15 N atom enriched) was added to each microcosm. Nitrogen movement from earthworm tissue to soil N [mineral N (NH 4 -N + NO 3 -N), dissolved organic N (DON) and organic N], microbial biomass N and plant shoot N pools was determined by destructive sampling at 1, 2, 4, 8 and 16 d. Earthworm tissues decomposed rapidly, and no tissue was visible after 4 d. Initially in pots without plants, most of the N from earthworm tissue was found in the organic N pool, however, as much as 55% of the N from decomposing earthworm tissue was incorporated into microbial biomass after 2 d. Much less of the N from earthworm tissue was transformed into DON and mineral N forms after 2 d. The DON and mineral N pools contained 13±18% and 4±7% of the N from earthworm tissue, respectively, from d 2 to 16. By the end of the experiment, N from earthworm tissue in the microbial biomass N pool declined to 29% while the amount of N from earthworm tissue in the organic N pool increased to 49%. The increase in the organic N may have resulted from the production of new organic compounds such as microbial by-products. In pots with plants, N from earthworm tissue was rapidly incorporated into microbial biomass, and by d 2, the microbial biomass N pool contained 40% of the N from earthworm tissue. Mineral N, DON and microbial biomass N concentrations were lower in pots with ryegrass seedlings compared to pots without plants, and after d 2 declined to almost undetectable amounts because of rapid plant uptake. Between 42±52% of the N from earthworm tissue was found in the organic N pool from d 1 to 8, and then declined to 19% by d 16. After 16 d, over 70% of the N added as earthworm tissue was incorporated into plant shoot biomass. Our results demonstrate that the movement of N from dead earthworm tissue into microbial biomass was extremely rapid, and in pots without plants, much of this N was transformed into organic N forms, while in pots with ryegrass, most of the N from earthworm tissue accumulated in ryegrass shoots.

In Vitro and In Vivo Anti-Inflammatory Activity of 17-O-Acetylacuminolide through the Inhibition of Cytokines, NF-κB Translocation and IKKβ Activity

BACKGROUND AND PURPOSE: 17-O-acetylacuminolide (AA), a diterpenoid labdane, was isolated for the first time from the plant species Neouvaria foetida. The anti-inflammatory effects of this compound were studied both in vitro and in vivo. EXPERIMENTAL APPROACH: Plant extracts were initially tested against LPS-stimulated release of tumor necrosis factor alpha (TNF-α) from murine macrophages (RAW264.7 cells). Based on bioassay-guided fractionation, the active compound was identified as AA. AA was tested for its ability to reduce nitric oxide (NO) production, and the inducible nitric oxide synthase (iNOS) expression. The inhibition of a panel of inflammatory cytokines (TNF, IL-1β, IL-6, KC, and GM-CSF) by AA was assessed at the expression and the mRNA levels. Moreover, the effect of AA on the translocation of the transcription factor nuclear factor kappa B (NF-κB) was evaluated in LPS-stimulated RAW264.7 cells and in TNF-stimulated L929 cells. Subsequently, AA was tested in the inhibitor of NF-κB kinase beta (IKKβ) activity assay. Lastly, the anti-inflammatory activity of AA in vivo was evaluated by testing TNF production in LPS-stimulated Balb/c mice. KEY RESULTS: AA effectively inhibited TNF-α release with an IC(50) of 2.7 µg/mL. Moreover, AA significantly inhibited both NO production and iNOS expression. It significantly and dose-dependently inhibited TNF and IL-1β proteins and mRNA expression; as well as IL-6 and KC proteins. Additionally, AA prevented the translocation of NF-κB in both cell lines; suggesting that it is acting at a post receptor level. This was confirmed by AA's ability to inhibit IKKβ activity, a kinase responsible for activating NF-κB, hence providing an insight on AA's mechanism of action. Finally, AA significantly reduced TNF production in vivo. CONCLUSIONS AND IMPLICATIONS: This study presents the potential utilization of this compound, as a lead for the development of an anti-inflammatory drug

Estimation and Mapping of Wet and Dry Mercury Deposition Across Northeastern North America

Whereas many ecosystem characteristics and processes influence mercury accumulation in higher trophic-level organisms, the mercury flux from the atmosphere to a lake and its watershed is a likely factor in potential risk to biota. Atmospheric deposition clearly affects mercury accumulation in soils and lake sediments. Thus, knowledge of spatial patterns in atmospheric deposition may provide information for assessing the relative risk for ecosystems to exhibit excessive biotic mercury contamination. Atmospheric mercury concentrations in aerosol, vapor, and liquid phases from four observation networks were used to estimate regional surface concentration fields. Statistical models were developed to relate sparsely measured mercury vapor and aerosol concentrations to the more commonly measured mercury concentration in precipitation. High spatial resolution deposition velocities for different phases (precipitation, cloud droplets, aerosols, and reactive gaseous mercury (RGM)) were computed using inferential models. An empirical model was developed to estimate gaseous elemental mercury (GEM) deposition. Spatial patterns of estimated total mercury deposition were complex. Generally, deposition was higher in the southwest and lower in the northeast. Elevation, land cover, and proximity to urban areas modified the general pattern. The estimated net GEM and RGM fluxes were each greater than or equal to wet deposition in many areas. Mercury assimilation by plant foliage may provide a substantial input of methyl-mercury (MeHg) to ecosystems.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/44443/1/10646_2004_Article_6259.pd