Inhibition of the rat adrenal ornithine decarboxylase activity by immobilization stress and/or dexamethasone

The effects of immobilization stress and/or dexamethasone (DEX) on the adrenal ornithine decarboxylase (ODC) activities of sham-operated and adrenal-medulloectomized (enucleated) male Sprague-Dawley rats were investigated. On day 11 after surgery, rats were injected with saline or DEX (1 mg/kg), 3 h before the time of sacrifice (0600 h or 1800 h). Four groups, from sham-operated and enucleated rats (ENU) treated with saline or DEX were subjected to immobilization stress for 1 h prior to sacrifice. Groups of rats from stress-sham-DEX, non stress-sham-DEX, stress-sham, non stress-sham, stress-ENU-DEX, non stress-ENU-DEX, stress-ENU, and non stress-ENU were sacrificed at 0600 h or 1800 h on day 11 after surgery. Adrenal glands were excised and later analyzed for ODC activities. Results indicated that DEX and/or immobilization stress inhibited ODC activities (p < 0.05) in normal and regenerating adrenal glands at 1800 h and ODC activity varies diurnally, the activity being greater at 1800 h than at 0600 hours (p < 0.001).     

Soil fauna diversity increases CO2 but suppresses N2O emissions from soil

Soil faunal activity can be a major control of greenhouse gas (GHG) emissions from soil. Effects of single faunal species, genera or families have been investigated, but it is unknown how soil fauna diversity may influence emissions of both carbon dioxide (CO₂, end product of decomposition of organic matter) and nitrous oxide (N₂O, an intermediate product of N transformation processes, in particular denitrification). Here, we studied how CO₂ and N₂O emissions are affected by species and species mixtures of up to eight species of detritivorous/fungivorous soil fauna from four different taxonomic groups (earthworms, potworms, mites, springtails) using a microcosm set‐up. We found that higher species richness and increased functional dissimilarity of species mixtures led to increased faunal‐induced CO₂ emission (up to 10%), but decreased N₂O emission (up to 62%). Large ecosystem engineers such as earthworms were key drivers of both CO₂ and N₂O emissions. Interestingly, increased biodiversity of other soil fauna in the presence of earthworms decreased faunal‐induced N₂O emission despite enhanced C cycling. We conclude that higher soil fauna functional diversity enhanced the intensity of belowground processes, leading to more complete litter decomposition and increased CO₂ emission, but concurrently also resulting in more complete denitrification and reduced N₂O emission. Our results suggest that increased soil fauna species diversity has the potential to mitigate emissions of N₂O from soil ecosystems. Given the loss of soil biodiversity in managed soils, our findings call for adoption of management practices that enhance soil biodiversity and stimulate a functionally diverse faunal community to reduce N₂O emissions from managed soils.     

Acclimation responses to temperature vary with vertical stratification: implications for vulnerability of soil‐dwelling species to extreme temperature events

The occurrence of summer heat waves is predicted to increase in amplitude and frequency in the near future, but the consequences of such extreme events are largely unknown, especially for belowground organisms. Soil organisms usually exhibit strong vertical stratification, resulting in more frequent exposure to extreme temperatures for surface‐dwelling species than for soil‐dwelling species. Therefore soil‐dwelling species are expected to have poor acclimation responses to cope with temperature changes. We used five species of surface‐dwelling and four species of soil‐dwelling Collembola that habituate different depths in the soil. We tested for differences in tolerance to extreme temperatures after acclimation to warm and cold conditions. We also tested for differences in acclimation of the underlying physiology by looking at changes in membrane lipid composition. Chill coma recovery time, heat knockdown time and fatty acid profiles were determined after 1 week of acclimation to either 5 or 20 °C. Our results showed that surface‐dwelling Collembola better maintained increased heat tolerance across acclimation temperatures, but no such response was found for cold tolerance. Concordantly, four of the five surface‐dwelling Collembola showed up to fourfold changes in relative abundance of fatty acids after 1 week of acclimation, whereas none of the soil‐dwelling species showed a significant adjustment in fatty acid composition. Strong physiological responses to temperature fluctuations may have become redundant in soil‐dwelling species due to the relative thermal stability of their subterranean habitat. Based on the results of the four species studied, we expect that unless soil‐dwelling species can temporarily retreat to avoid extreme temperatures, the predicted increase in heat waves under climatic change renders these soil‐dwelling species more vulnerable to extinction than species with better physiological capabilities. Being able to act under a larger thermal range is probably costly and could reduce maximum performance at the optimal temperature.     

Herbivore trampling as an alternative pathway for explaining differences in nitrogen mineralization in moist grasslands

Studies addressing the role of large herbivores on nitrogen cycling in grasslands have suggested that the direction of effects depends on soil fertility. Via selection for high quality plant species and input of dung and urine, large herbivores have been shown to speed up nitrogen cycling in fertile grassland soils while slowing down nitrogen cycling in unfertile soils. However, recent studies show that large herbivores can reduce nitrogen mineralization in some temperate fertile soils, but not in others. To explain this, we hypothesize that large herbivores can reduce nitrogen mineralization in loamy or clay soils through soil compaction, but not in sandy soils. Especially under wet conditions, strong compaction in clay soils can lead to periods of soil anoxia, which reduces decomposition of soil organic matter and, hence, N mineralization. In this study, we use a long-term (37-year) field experiment on a salt marsh to investigate the hypothesis that the effect of large herbivores on nitrogen mineralization depends on soil texture. Our results confirm that the presence of large herbivores decreased nitrogen mineralization rate in a clay soil, but not in a sandy soil. By comparing a hand-mown treatment with a herbivore-grazed treatment, we show that these differences can be attributed to herbivore-induced changes in soil physical properties rather than to above-ground biomass removal. On clay soil, we find that large herbivores increase the soil water-filled porosity, induce more negative soil redox potentials, reduce soil macrofauna abundance, and reduce decomposition activity. On sandy soil, we observe no changes in these variables in response to grazing. We conclude that effects of large herbivores on nitrogen mineralization cannot be understood without taking soil texture, soil moisture, and feedbacks through soil macrofauna into account.     

Ethylene based on woody biomass—what are environmental key issues of a possible future Swedish production on industrial scale

Purpose

In order to reduce its environmental impact, the chemical industry no longer produces base chemicals such as ethylene, solely from fossil, but also from biomass-based feedstocks. However, a biomass option suitable for one region might not be as suitable for another region due to, e.g., long transport and the related environmental. Therefore, local biomass alternatives and the environmental impact related to the production of chemicals from these alternatives need to be investigated. This study assesses the environmental impact of producing ethylene from Swedish wood ethanol.

Methods

The study was conducted following the methodology of life cycle assessment. The life cycle was assessed using a cradle-to-gate perspective for the production of 50,000 tonnes ethylene/year for the impact categories global warming, acidification (ACP), photochemical ozone creation, and eutrophication (EP).

Results and discussion

The production of enzymes used during the life cycle had a significant effect on all investigated impacts. However, reduced consumption of enzyme product, which could possibly be realized considering the rapid development of enzymes, lowered the overall environmental impact of the ethylene. Another approach could be to use alternative hydrolyzing agents. However, little information on their environmental impact is available. An additional key contributor, with regard to ACP, EP, and POCP, was the ethanol production. Therefore, further improvements with regard to the process’ design may have beneficial effects on its environmental impact.

Conclusions

The study assessed the environmental impact of wood ethylene and pointed to several directions for improvements, such as improved enzyme production and reduced consumption of enzyme products. Moreover, the analysis showed that further investigations into other process options and increase of ethylene production from biomass are worth continued research.     

Dynamin is required for the activation of mitogen-activated protein (MAP) kinase by MAP kinase kinase

Internalization of activated receptors from the plasma membrane has been implicated in the activation of mitogen-activated protein (MAP) kinase. However, the mechanism whereby membrane trafficking may regulate mitogenic signaling remains unclear. Here we report that dominant-negative dynamin (K44A), an inhibitor of endocytic vesicle formation, abrogates MAP kinase activation in response to epidermal growth factor, lysophosphatidic acid, and protein kinase C-activating phorbol ester. In contrast, dynamin-K44A does not affect the activation of Ras, Raf, and MAP kinase kinase (MEK) by either agonist. Through immunofluorescence and subcellular fractionation studies, we find that activated MEK is present both at the plasma membrane and in intracellular vesicles but not in the cytosol. Our findings suggest that dynamin-regulated endocytosis of activated MEK, rather than activated receptors, is a critical event in the MAP kinase activation cascade.     

Connexin-43 interactions with ZO-1 and alpha- and beta-tubulin

Gap junctions are composed of connexins that form transmembrane channels between adjacent cells. The C-terminal tail of connexin-43 (Cx43), the most widely expressed connexin member, has been implicated in the regulation of Cx43 channel gating. Interestingly, channel-independent processes regulated by Cx43 have also been postulated. In our studies to elucidate the mechanism of Cx43 channel gating by growth factors and to explore additional functions of gap junctions, we have identified three interacting partners of the C-terminal tail of Cx43 (Cx43CT). (i) the c-Src tyrosine kinase, which phosphorylates Cx43CT and is involved in G protein-mediated inhibition of Cx43 gap junctional communication. (ii) the ZO-1 'scaffold' protein, which might recruit signaling proteins into Cx43-based gap junctions. (iii) microtubules (consisting of alpha/beta-tubulin dimers), which extend with their distal ends to Cx43-based gap junctions, suggesting that Cx43 gap junctions may play a novel role in regulating microtubule stability in contacted cells. Here we show that Cx43 binds alpha-tubulin equally well as beta-tubulin. In addition, we show that the second, but not the first, PDZ domain of ZO-1 binds directly to Cx43, and we confirm that the very C-terminal isoleucine residue of Cx43 is critical for ZO-1 binding.     

Synthesis, solution structure analysis and antibody binding of cyclic epitope peptides from glycoprotein D of Herpes simplex virus type I

Two cyclic peptides with a thioether bond have been synthesised corresponding to the 9-22 (9LKMADPNRFRGKDL(22)) sequence of glycoprotein D (gD-1) of Herpes simplex virus. The role of the secondary structure in protein-specific monoclonal antibody recognition was investigated. The sequence selected for this study comprises a strongly antigenic site adopting a beta-turn at residues 14Pro-(15)Asn. Thioether bond was formed between the free thiol group of cysteine or homocysteine inserted in position 11 and the chloroacetylated side chain of lysine in position 18. We report here the preparation of cyclic peptides containing Cys or Hcy in position 11, differing only in one methylene group. The linear precursor peptides were synthesised by Boc/Bzl strategy on MBHA resin, and the cyclisation was carried out in alkaline solution. The secondary structure of the peptides was studied by CD, FT-IR and NMR spectroscopy. The CD and FT-IR data have revealed fundamental changes in the solution conformation of the two compounds. The CH(2) group difference significantly resulted in the altered turn structure at the 12Ala and 13Asp as identified by NMR spectroscopy. The antibody binding properties of the cyclopeptides studied by gD-specific monoclonal antibody (A16) in direct and competition enzyme-linked immunosorbent assay (ELISA) were also not the same. We found that peptide LK[HcyADPNRFK]GKDL exhibited higher affinity to Mab A16 than peptide LK[CADPNRFK]GKDL, however, their reactivity was significantly lower compared to the linear ones. Our results clearly show the importance of secondary structure in an antibody binding and demonstrate that even a slight modification of the primary structure dramatically could influence the immune recognition of the synthetic antigens.