Effects of mesophyll conductance on vegetation responses to elevated CO2 concentrations in a land surface model

Mesophyll conductance (g_m) is known to affect plant photosynthesis. However, g_m is rarely explicitly considered in land surface models (LSMs), with the consequence that its role in ecosystem and large‐scale carbon and water fluxes is poorly understood. In particular, the different magnitudes of g_m across plant functional types (PFTs) are expected to cause spatially divergent vegetation responses to elevated CO₂ concentrations. Here, an extensive literature compilation of g_m across major vegetation types is used to parameterize an empirical model of g_m in the LSM JSBACH and to adjust photosynthetic parameters based on simulated A_n ? C_i curves. We demonstrate that an explicit representation of g_m changes the response of photosynthesis to environmental factors, which cannot be entirely compensated by adjusting photosynthetic parameters. These altered responses lead to changes in the photosynthetic sensitivity to atmospheric CO₂ concentrations which depend both on the magnitude of g_m and the climatic conditions, particularly temperature. We then conducted simulations under ambient and elevated (ambient + 200 μmol/mol) CO₂ concentrations for contrasting ecosystems and for historical and anticipated future climate conditions (representative concentration pathways; RCPs) globally. The g_m‐explicit simulations using the RCP8.5 scenario resulted in significantly higher increases in gross primary productivity (GPP) in high latitudes (+10% to + 25%), intermediate increases in temperate regions (+5% to + 15%), and slightly lower to moderately higher responses in tropical regions (?2% to +5%), which summed up to moderate GPP increases globally. Similar patterns were found for transpiration, but with a lower magnitude. Our results suggest that the effect of an explicit representation of g_m is most important for simulated carbon and water fluxes in the boreal zone, where a cold climate coincides with evergreen vegetation.     

ADSORPTION OF FULVIC ACID ON ALGAL SURFACES AND ITS EFFECT ON CARBON UPTAKE

Adsorption of Suwannee River fulvic acid (SRFA) to algal surfaces of three green algae was studied at environmentally relevant pH values (4 –7) and SRFA concentrations (5–100 mg·L ^{− 1}). The influence of adsorbed SRFA on carbon uptake of Scenedesmus subspicatus Chodat was also examined. Although no adsorption was observed at neutral pH values (pH 6 and 7), at pH 4 up to 31 mg SRFA·m ^{− 2} and at pH 5 up to 4 mg SRFA·m ^{− 2} was adsorbed to the algal surfaces. Electrophoretic mobility measurements of S. subspicatus demonstrated an increase in the negative surface charge of the alga in the presence of SRFA at pH 4. The adsorbed SRFA also influenced ¹⁴C uptake in S. subspicatus; in this case, enhanced carbon uptake could be related to the amount of adsorbed SRFA. The binding of humic substances by algal surfaces was interpreted as the result of hydrogen bonding and hydrophobic interactions.     

Trace metals in large agglomerates (marine snow)

Marine agglomerates were collected by SCUBA from surface watersof Monterey Bay, California and one coastal site 100 km offPoint Sur, California using trace metal clean techniques. Concentrationsof Al, Fe, Mn, Cu, Ni, Zn, Cd and Pb were measured for bothweak acid soluble and refractory metals and compared to suspendmaterial collected in water bottles at the same locations. Gravimetricanalysis of agglomerate and surrounding suspended particulatematter indicated that although agglomerates represented <0.1%of total water sample volume (determined photographically),they contained up to 50% of the total particulate dry weight;trace metal concentrations in the agglomerate fraction werealso disproportionately high. Agglomerates collected withinMonterey Bay contained large quantitites of inorganic material(>40% dry weight), with most of the associated metals containedprimarily within the refractory fraction. In contrast, the offshorestation agglomerates contained <0.3% inorganic material withmetals primarily associated with the weak acid soluble fraction.Both the metal concentrations and leach characteristics of theoffshore station suggest that these agglomerates were comprisedof an active phytoplankton assemblage highly enriched in Cd.Metal concentrations in the offshore samples in conjunctionwith agglomerate abundance indicate that agglomerates may bea major transporter of trace metals out of the euphotic zone.     

Action spectrum for the in vitro induction of simian virus 40 by ultraviolet radiation

A line of simian virus 40-transformed hamster kidney cells was exposed to ultraviolet radiation at eleven different wavelengths in the region 238-302 nm. An action spectrum derived from the resulting exposure-response curves for the induction of simian virus 40 from these cells exhibits a broad peak in the region 260-270 nm suggesting DNA as the major chromophore for this response. This conclusion is consistent with results obtained by other investigators who have noted viral induction by a number of DNA-damaging agents.     

Mechanism of human lymphotoxin and tumor necrosis factor induced destruction of cells in vitro: phospholipase activation and deacylation of specific-membrane phospholipids

The role of phospholipase (PLase) activation and lipid metabolism in lymphotoxin (LT)- and tumor necrosis factor (TNF)-mediated destruction of murine L929 cells was examined. At the levels of LT and TNF employed, cell destruction began at 4-6 h and was 99% complete by 30 h. Cell membrane phospholipids (PL), labelled in situ at the C2 position with 14C arachidonic acid, were analyzed by two-dimensional thin-layer chromatography and quantitated over a 30 h time course after LT or TNF treatment. The ratio of radiolabel incorporation relative to the actual amount of each PL present was determined by inorganic phosphate analysis. Radiolabelled arachidonic acid, eicosanoids, and neutral lipids were released into the medium prior to the onset of cell death (4-6 h) and continued to accumulate linearly throughout the destructive reaction. There was a quantitative relationship between the appearance of radiolabelled metabolites in the media and the loss of radiolabelled cellular PL. Cellular phosphatidylethanolamine was the primary PL deacylated by PLase action, showing a 75% reduction in radiolabel. The PLase inhibitors--quinacrine, hydrocortisone, dexamethasone, and indomethacin--were potent inhibitors of LT- and TNF-mediated cell destruction, suggesting that selective deacylation of specific membrane PL by PLase activation is an important step in the events that lead to LT- and TNF-mediated cellular destruction in vitro.     

Assembly and aggregation properties of synthetic Alzheimer's A4/beta amyloid peptide analogs.

The amyloid A4 or beta peptide is a major component of extracellular amyloid deposits that are a characteristic feature of Alzheimer's disease. We synthesized a series of peptide analogs of the A4/beta peptide which are progressively longer at their carboxyl termini, including 42- and 39-residue peptides which represent the major forms of the A4/beta peptide in senile plaque and the hereditary cerebral hemorrhage with amyloidosis form, respectively. All peptides tested, beta 1-28 through beta 1-42, formed amyloid-like fibrils and previously unreported thin sheet-like structures which stained with thioflavin T and Congo Red. The solubility of beta 1-42 and shorter peptides was pH and concentration dependent, with a broad insolubility profile in the pH range of 3.5-6.5 and at concentrations above 0.75 mg/ml. Only peptides of 42 residues or longer were significantly insoluble at pH 7.4. beta 1-47 and beta 1-52 peptides are highly insoluble in aqueous media but are soluble at 40 mg/ml in the alpha helix-promoting solvent, 1,1,1,3,3,3-hexafluoro-2-propanol. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed that the beta 1-42 peptide migrates as a series of higher molecular mass aggregates whereas shorter peptides migrate as monomers. Aggregation is also dependent on pH, peptide concentration, and time of incubation in aqueous medium. These results indicate that the length of the hydrophobic carboxyl terminus of the A4/beta peptide is important in determining the solubility and aggregation properties of the A4/beta peptide and that acid pH environment, high peptide concentration, and long incubation time would be predicted to be important factors in promoting amyloid deposition.     

Differential phosphoproteome profiling reveals a functional role for VASP in Helicobacter pylori-induced cytoskeleton turnover in gastric epithelial cells

Infection with Helicobacter pylori induces various gastric diseases, including ulceration, gastritis and neoplasia. As H. pylori-induced cellular mechanisms leading to these disease states are widely unclear, we analysed the phosphoproteome of H. pylori-infected gastric epithelial cells. Phosphoproteins from infected cells were enriched using affinity columns and analysed by two-dimensional gel electrophoresis and mass spectrometry. Eleven novel phosphoproteins that showed differentially regulated phosphorylation levels during H. pylori infection were identified. Interestingly, the identified proteins were actin-binding, transport and folding, RNA/DNA-binding or cancer-associated proteins. We analysed functions of one identified H. pylori-regulated candidate, the vasodilator-stimulated phosphoprotein (VASP). H. pylori induced VASP phosphorylation at residues Ser157, Ser239 and Thr278, which was enhanced by the bacterial oncogene cytotoxin-associated gene A. Overexpression of a phosphorylation-resistant VASP mutant efficiently blocked host cell elongation. We identified cGMP-dependent protein kinase G-mediated Ser239 and Thr278 phosphorylation of VASP as a crucial event in H. pylori-dependent host cell elongation. These results suggest that phosphorylated VASP could be a novel target candidate for therapeutic intervention in H. pylori-related gastric diseases.     

Peptidic nanoparticles: for cancer diagnosis and therapy

A challenging topic in cancer research is to create drug delivery system that can bring in a specific and noncytotoxic manner a therapeutic compound. Usually, tumor targeting requires very specific compounds. Currently, peptide analogues like somatostatin, neurotensin, or bombesin are used to target G-coupled receptors, which are overexpressed on tumor cells. However, many of those analogues are rapidly degraded in the plasma and are cytotoxic [1–2]. Due to the limited efficiency and high toxicity of conventional chemotherapy different strategies have been developed for non-cytotoxic cancer treatment and cancer localization [3–5]. The recent development in bio-nanotechnology offers new avenues for cancer therapy. A lot of studies have been devoted to nanoparticulate delivery systems (10–100nm) like lipid or polymer particles [6–8]. Due to the nanometer sized of such cargos, the transportation of therapeutic compounds in the blood stream is increased in terms of time circulation. But their surface functionalization to improve drug-targeting properties is usually complicated and rather uneffective. We have recently designed a novel type of functional nanoparticles with regular icosahedral symmetry, mimicking small, rigid viral capsids (Fig. 1 (A)) and a diameter of about 17 nm (Fig. 1 (C)) which self-assemble from single polypeptide chains (Fig. 1 (B)).