Combustion influences on natural abundance nitrogen isotope ratio in soil and plants following a wildfire in a sub-alpine ecosystem

This before-and-after-impact study uses the natural abundance N isotope ratio (δ¹⁵N) to investigate the effects of a wildfire on sub-alpine ecosystem properties and processes. We measured the ¹⁵N signatures of soil, charred organic material, ash and foliage in three sub-alpine plant communities (grassland, heathland and woodland) in south-eastern Australia. Surface bulk soil was temporarily enriched in ¹⁵N immediately after wildfire compared to charred organic material and ash in all plant communities. We associated the enrichment of bulk soil with fractionation of N during combustion and volatilization of N, a process that also explains the sequential enrichment of ¹⁵N of unburnt leaves > ash > charred organic material in relation to duration and intensity of heating. The rapid decline in ¹⁵N of bulk soil to pre-fire values indicates that depleted ash, containing considerable amounts of total N, was readily incorporated into the soil. Foliar δ¹⁵N also increased with values peaking 1 year post-fire. Foliar enrichment was foremost coupled with the release of enriched NH₄ ⁺ into the soil owing to isotopic discrimination during volatilization of soluble N and combustion of organic material. The mode of post-fire regeneration influenced foliar ¹⁵N enrichment in two species indicating use of different sources of N following fire. The use of natural abundance of ¹⁵N in soil, ash and foliage as a means of tracing transformation of N during wildfire has established the importance of combustion products as an important, albeit temporary source of inorganic N for plants regenerating after wildfire.     

Structural and Functional Analysis of the Natural JNK1 Inhibitor Quercetagetin

c-Jun NH2-terminal kinases (JNKs) and phosphatidylinositol 3-kinase (PI3-K) play critical roles in chronic diseases such as cancer, type II diabetes, and obesity. We describe here the binding of quercetagetin (3,3′,4′,5,6,7-hydroxyflavone), related flavonoids, and SP600125 to JNK1 and PI3-K by ATP-competitive and immobilized metal ion affinity-based fluorescence polarization assays and measure the effect of quercetagetin on JNK1 and PI3-K activities. Quercetagetin attenuated the phosphorylation of c-Jun and AKT, suppressed AP-1 and NF-κB promoter activities, and also reduced cell transformation. It attenuated tumor incidence and reduced tumor volumes in a two-stage skin carcinogenesis mouse model.Our crystallographic structure determination data show that quercetagetin binds to the ATP-binding site of JNK1. Notably, the interaction between Lys55, Asp169, and Glu73 of JNK1 and the catechol moiety of quercetagetin reorients the N-terminal lobe of JNK1, thereby improving compatibility of the ligand with its binding site. The results of a theoretical docking study suggest a binding mode of PI3-K with the hydroxyl groups of the catechol moiety forming hydrogen bonds with the side chains of Asp964 and Asp841 in the p110γ catalytic subunit. These interactions could contribute to the high inhibitory activity of quercetagetin against PI3-K. Our study suggests the potential use of quercetagetin in the prevention or therapy of cancer and other chronic diseases.     

Novel Cultivation-Based Approach To Understanding the Miscellaneous Crenarchaeotic Group (MCG) Archaea from Sedimentary Ecosystems

The uncultured miscellaneous crenarchaeotic group (MCG) archaea comprise one of the most abundant microbial groups in the Earth''s subsurface environment. However, very little information is available regarding the lifestyle, physiology, and factors controlling the distribution of members of this group. We established a novel method using both cultivation and molecular techniques, including a pre-PCR propidium monoazide treatment, to investigate viable members of the MCG in vitro. Enrichment cultures prepared from estuarine sediment were provided with one of a variety of carbon substrates or cultivation conditions and incubated for 3 weeks. Compared with the samples from time zero, there was an order-of-magnitude increase in the number of MCG 16S rRNA genes in almost all cultures, indicating that MCG archaea are amenable to in vitro cultivation. None of the tested substrates or conditions significantly stimulated growth of MCG archaea more than the basal medium alone; however, glycerol (0.02%) had a significantly inhibitory effect (P < 0.05). Diversity analysis of populations resulting from four culture treatments (basal medium, addition of amino acids, H₂-CO₂ as the gas phase, or initial aerobic conditions) revealed that the majority of viable MCG archaea were affiliated with the MCG-8 and MCG-4 clusters. There were no significant differences in MCG diversity between these treatments, also indicating that some members of MCG-4 and MCG-8 are tolerant of initially oxic conditions. The methods outlined here will be useful for further investigation of MCG archaea and comparison of substrates and cultivation conditions that influence their growth in vitro.     

Palynology of the perigoniate Aroideae: Zamioculcas,Gonatopus and Stylochaeton (Araceae)

The pollen of the perigoniate Aroideae sensu Mayo et al. (1997) ( Zamioculcas Schott, Gonatopus Hook. f. ex Engl. and Stylochaeton Lepr.) differs ultrastructurally from that of the aperigoniate Aroideae in several important exine and aperture characters. The almost identical zona-aperturate pollen of Zamioculcas and Gonatopus has outside the aperture an elaborated, thick ectexine, while the aperture consists of a thin, but continuous ectexine and a thick, lamellate endexine. In contrast, the omniaperturate pollen of Stylochaeton has a thin, not clearly stratified ectexine and a thin, heterogeneous endexine below. However, the zona-aperturate pollen of Zamioculcas and Gonatopus deviates significantly from the superficially similar zona-aperturate pollen of the unrelated Monstereae (e. g., Monstera Adans., Amydrium Schott): in the apertures of Monstera or Amydrium both the thin, but continuous ectexine and the lamellate endexine, which are typical features for Zamioculcas and Gonatopus , are absent. The palynological data underline not only the present classification of Zamioculcas , Gonatopus and of Stylochaeton into two tribes (Zamioculcadeae and Stylochaetoneae) and the differences of both tribes from the other Aroideae, but show also significant deviations in the respective zona-aperturate condition in Monstereae (Monsteroideae) and Zamioculcadeae (Aroideae).     

Three-Dimensional Protein Fold Determination from Backbone Amide Pseudocontact Shifts Generated by Lanthanide Tags at Multiple Sites

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Spontaneous Atopic Dermatitis-Like Symptoms in a/a ma ft/ma ft/J Flaky Tail Mice Appear Early after Birth

Loss-of-function mutations in human profilaggrin gene have been identified as the cause of ichthyosis vulgaris (IV), and as a major predisposition factor for atopic dermatitis (AD). Similarly, flaky tail (a/a ma ft/ma ft/J) mice were described as a model for IV, and shown to be predisposed to eczema. The aim of this study was to correlate the flaky tail mouse phenotype with human IV and AD, in order to dissect early molecular events leading to atopic dermatitis in mice and men, suffering from filaggrin deficiency. Thus, 5-days old flaky tail pups were analyzed histologically, expression of cytokines was measured in skin and signaling pathways were investigated by protein analysis. Human biopsies of IV and AD patients were analyzed histologically and by real time PCR assays. Our data show acanthosis and hyperproliferation in flaky tail epidermis, associated with increased IL1β and thymic stromal lymphopoietin (TSLP) expression, and Th2-polarization. Consequently, NFκB and Stat pathways were activated, and IL6 mRNA levels were increased. Further, quantitative analysis of late epidermal differentiation markers revealed increased Small proline-rich protein 2A (Sprr2a) synthesis. Th2-polarization and Sprr2a increase may result from high TSLP expression, as shown after analysis of 5-days old K14-TSLP tg mouse skin biopsies. Our findings in the flaky tail mouse correlate with data obtained from patient biopsies of AD, but not IV. We propose that proinflammatory cytokines are responsible for acanthosis in flaky tail epidermis, and together with the Th2-derived cytokines lead to morphological changes. Accordingly, the a/a ma ft/ma ft/J mouse model can be used as an appropriate model to study early AD onset associated with profilaggrin deficiency.     

Alcohol regulates eukaryotic elongation factor 2 phosphorylation via an AMP-activated protein kinase-dependent mechanism in C2C12 skeletal myocytes

Ethanol decreases protein synthesis in cells, although the underlying regulatory mechanisms of this process are not fully established. In the present study incubation of C2C12 myocytes with 100 mm EtOH decreased protein synthesis while markedly increasing the phosphorylation of eukaryotic elongation factor 2 (eEF2), a key component of the translation machinery. Both mTOR and MEK pathways were found to play a role in regulating the effect of EtOH on eEF2 phosphorylation. Rapamycin, an inhibitor of mammalian target of rapamycin, and the MEK inhibitor PD98059 blocked the EtOH-induced phosphorylation of eEF2, whereas the p38 MAPK inhibitor SB202190 had no effect. Unexpectedly, EtOH decreased the phosphorylation and activity of the eEF2 upstream regulator eEF2 kinase. Likewise, treatment of cells with the inhibitor rottlerin did not block the stimulatory effect of EtOH on eEF2, suggesting that eEF2 kinase (eEF2K) does not play a role in regulating eEF2. In contrast, increased eEF2 phosphorylation was correlated with an increase in AMP-activated protein kinase (AMPK) phosphorylation and activity. Compound C, an inhibitor of AMPK, suppressed the effects of EtOH on eEF2 phosphorylation but had no effect on eEF2K, indicating that AMPK regulates eEF2 independent of eEF2K. Finally, EtOH decreased protein phosphatase 2A activity when either eEF2 or AMPK was used as the substrate. Thus, this later action may partially account for the increased phosphorylation of eEF2 in response to EtOH and the observed sensitivity of AMPK to rapamycin and PD98059 treatments. Collectively, the induction of eEF2 phosphorylation by EtOH is controlled by an increase in AMPK and a decrease in protein phosphatase 2A activity.