Stability of grassland production is robust to changes in the consumer food web

Theory predicts that consumers may stabilise or destabilise plant production depending on model assumptions, and tests in aquatic food webs suggest that trophic interactions are stabilising. We quantified the effects of trophic interactions on temporal variability (standard deviation) and temporal stability (mean/standard deviation) of grassland biomass production and the plant diversity–stability relationship by experimentally removing heterotrophs (large vertebrates, arthropods, foliar and soil fungi) from naturally and experimentally assembled grasslands of varying diversity. In both grassland types, trophic interactions proportionately decreased plant community biomass mean and variability over the course of 6 years, leading to no net change in temporal stability or the plant diversity–stability relationship. Heterotrophs also mediated plant coexistence; their removal reduced diversity in naturally assembled grasslands. Thus, herbivores and fungi reduce biomass production, concurrently reducing the temporal variability of energy and material fluxes. Because of this coupling, grassland stability is robust to large food web perturbations.     

Role of Se(VI) in counteracting oxidative damage in <Emphasis Type="Italic">Brassica juncea</Emphasis> L. under Cr(VI) stress

Chromium (Cr) is considered to be one of the major environmental hazards and poses a threat to both plant and animal health. Selenium (Se), however, has been recognized as an essential micronutrient in plants. To understand the role of Se(VI) in oxidative stress management and regulation of antioxidative defence mechanism against heavy metal stress, the seedlings of Brassica juncea L. were raised in Petri plates containing nutrient media supplemented with only with Se(VI) and Cr(VI), or their combination. It was observed that of Cr(VI) causes an increase in reactive oxygen species (ROS) in the seedlings leading to oxidative stress. Histological studies using confocal and visible microscopy confirmed the biochemical results. Supplementation of up to 4 µM of Se(VI) to media containing 300 µM of Cr(VI) reduced the contents of ROS and increased enzymatic and non-enzymatic antioxidants in the seedlings. At a concentration of 6 µM, however, Se(VI) was toxic. The results suggested that at appropriate concentrations, the exogenous application of Se(VI) enabled the B. juncea seedlings to counteract the effects of Cr(VI), thereby increasing the resistance of plants.     

Role of root-mediated interactions in phytotoxic interference of Ageratum conyzoides with rice (Oryza sativa)

Ageratum conyzoides L. (billy goat weed; Asteraceae) is an annual invasive weed native of tropical America and has now naturalized worldwide, particularly in Southeast Asia. The present study investigated the nature and potential of root-mediated allelopathic interference of A. conyzoides against rice (Oryza sativa). Root and shoot length and biomass accumulation of rice were significantly reduced (by 18–30%) when grown in the rhizosphere soil of the weed indicating the release of putative allelochemicals from the weed into the soil. The growth of rice was also progressively reduced in the soil amended with increasing amounts of root residues (5, 10 and 20 g kg⁻¹ soil) of A. conyzoides. The addition of activated charcoal, an inert material with high affinity for organic biomolecules, partly ameliorated the negative effects of root residues amended in the soil. Further, there was no negative effect on the availability of soil nutrients in the root-amended soils. These were rather nutrient rich with greater electrical conductivity, and higher amount of organic matter, thus indicating no role in observed growth reduction. The reduction in allelopathic effects of root residue upon charcoal addition further indicated that putative phytotoxins released from the weed roots are water-soluble phenolic compounds. A significant amount of water-soluble phenolics were present in rhizosphere (∼6-times higher) and root-amended soils (∼5–10-fold higher) and their content was reduced (to ∼3.6–7.0-fold higher) when charcoal was added. The observed growth reduction in Ageratum rhizospheric or root-amended soils was concomitant with the amount of phenolic compounds. Upon HPLC analyses, these were identified as p-coumaric acid, gallic acid, ferulic acid, p-hydroxybenzoic acid and anisic acid. Under laboratory conditions, these phenolic acids reduced the root length and seedling weight of rice individually as well as in equimolar mixture, though no synergistic effect was noticed. The study concludes that root exudates and residues of A. conyzoides suppress the growth of rice by releasing phenolic allelochemicals into the soil rhizosphere and not through alteration of soil nutrients, and allelopathy plays a significant role in root-mediated negative interference of A. conyzoides.     

Atomic structure of the major capsid protein of rotavirus: implications for the architecture of the virion

The structural protein VP6 of rotavirus, an important pathogen responsible for severe gastroenteritis in children, forms the middle layer in the triple-layered viral capsid. Here we present the crystal structure of VP6 determined to 2 A resolution and describe its interactions with other capsid proteins by fitting the atomic model into electron cryomicroscopic reconstructions of viral particles. VP6, which forms a tight trimer, has two distinct domains: a distal beta-barrel domain and a proximal alpha-helical domain, which interact with the outer and inner layer of the virion, respectively. The overall fold is similar to that of protein VP7 from bluetongue virus, with the subunits wrapping about a central 3-fold axis. A distinguishing feature of the VP6 trimer is a central Zn(2+) ion located on the 3-fold molecular axis. The crude atomic model of the middle layer derived from the fit shows that quasi-equivalence is only partially obeyed by VP6 in the T = 13 middle layer and suggests a model for the assembly of the 260 VP6 trimers onto the T = 1 viral inner layer.     

Improving the developability of an anti-EphA2 single-chain variable fragment for nanoparticle targeting

Antibody-targeted nanoparticles have great promise as anti-cancer drugs; however, substantial developmental challenges of antibody modules prevent many candidates from reaching the clinic. Here, we describe a robust strategy for developing an EphA2-targeting antibody fragment for immunoliposomal drug delivery. A highly bioactive single-chain variable fragment (scFv) was engineered to overcome developmental liabilities, including low thermostability and weak binding to affinity purification resins. Improved thermostability was achieved by modifying the framework of the scFv, and complementarity-determining region (CDR)-H2 was modified to increase binding to protein A resins. The results of our engineering campaigns demonstrate that it is possible, using focused design strategies, to rapidly improve the stability and manufacturing characteristics of an antibody fragment for use as a component of a novel therapeutic construct.     

Phenolic allelochemicals released by <Emphasis Type="Italic">Chenopodium murale</Emphasis> affect the growth,nodulation and macromolecule content in chickpea and pea

The present study was conducted to investigate the effect of the residue of Chenopodium murale L. on growth, nodulation and macromolecule content of two legume crops, viz., Cicer arietinum L. (chickpea) and Pisum sativum L. (pea). A significant reduction in root and shoot length as well as dry matter accumulation occurred when both the legumes were grown in the soil amended with 5, 10, 20 and 40 g residue kg⁻¹ soil. In general, a gradual decline in growth was associated with an increasing amount of residues in the soil. There was also a significant reduction in total chlorophyll content and the amounts of protein and carbohydrates (macromolecules) in plants growing in the residue-amended soil. The nodulation was completely absent in chickpea and pea when the plants were grown in the soil amended with 10 and 20 g residue kg⁻¹ soil, respectively. At a lower rate of residue amendment (5 g kg⁻¹ soil), a significant decline in nodule number and weight, and leghaemoglobin content was recorded. Root oxidizability, an indirect measure of tissue viability and cellular respiration, was adversely affected in both the legumes under various treatments of residue amendment. The observed growth reduction concomitant with increased proline accumulation indicated the presence of some inhibitory compounds in the residue-amended soil. It was rich in phenolics identified as protocatechuic, ferulic, p-coumaric and syringic acid with 12.8, 30.4, 20.2 and 33.6% relative content, respectively. The results suggest that the residue of C. murale releases phenolic allelochemicals, which deleteriously affect the growth, nodulation and macromolecule content of chickpea and pea.     

Protectin D1 is generated in asthma and dampens airway inflammation and hyperresponsiveness

Protectins are newly identified natural chemical mediators that counter leukocyte activation to promote resolution of inflammation. In this study, we provide the first evidence for protectin D1 (PD1, 10R,17S-dihydroxy-docosa-4Z,7Z,11E,13E,15Z,19Z-hexaenoic acid) formation from docosahexaenoic acid in human asthma in vivo and PD1 counterregulatory actions in allergic airway inflammation. PD1 and 17S-hydroxy-docosahexaenoic acid were present in exhaled breath condensates from healthy subjects. Of interest, levels of PD1 were significantly lower in exhaled breath condensates from subjects with asthma exacerbations. PD1 was also present in extracts of murine lungs from both control animals and those sensitized and aerosol challenged with allergen. When PD1 was administered before aeroallergen challenge, airway eosinophil and T lymphocyte recruitment were decreased, as were airway mucus, levels of specific proinflammatory mediators, including IL-13, cysteinyl leukotrienes, and PGD(2), and airway hyperresponsiveness to inhaled methacholine. Of interest, PD1 treatment after aeroallergen challenge markedly accelerated the resolution of airway inflammation. Together, these findings provide evidence for endogenous PD1 as a pivotal counterregulatory signal in allergic airway inflammation and point to new therapeutic strategies for modulating inflammation in asthmatic lung.     

Mitochondrial reactive oxygen species signal hepatocyte steatosis by regulating the phosphatidylinositol 3-kinase cell survival pathway

Abnormal dietary intake of macronutrients is implicated in the development of obesity and fatty liver disease. Steatosis develops in cultured hepatocytes exposed to medium containing either a high concentration of long chain free fatty acids (HFFA) or medium deficient in methionine and choline (MCD). This study examined the mitochondrial reactive oxygen species (ROS)-dependent regulation of the phosphoinositol (PI) 3-kinase pathway in steatosis induced by exposure of AML-12 mouse hepatocytes to MCD or HFFA medium. Exposure to either MCD or HFFA medium resulted in increased production of superoxide anions and H(2)O(2), transduction of the PI 3-kinase pathway and steatosis. Inhibition of PI 3-kinase with LY294002 prevented steatosis. Pharmacologically inhibiting electron transport chain complex III production of ROS prevented activation of PI 3-kinase during macronutrient perturbation, whereas pharmacologically promoting electron transport chain complex III ROS production activated PI 3-kinase independent of nutrient input. The data suggest that H(2)O(2) is the ROS species involved in signal transduction; promoting the rapid conversion of superoxide to H(2)O(2) does not inhibit PI 3-kinase pathway activation during nutrient perturbation, and exogenous H(2)O(2) activates it independent of nutrient input. In addition to transducing PI 3-kinase, the ROS-dependent signal cascade amplifies the PI 3-kinase signal by maintaining phosphatase and tensin homolog in its inactive phosphorylated state. Knockdown of phosphatase and tensin homolog by small interfering RNA independently activated the PI 3-kinase pathway. Our findings suggest a common path for response to altered nutrition involving mitochondrial ROS-dependent PI 3-kinase pathway regulation, leading to steatosis.     

Biofilm Formation by and Antifungal Susceptibility of Candida Isolates from Urine

Biofilm formation (BF) in the setting of candiduria has not been well studied. We determined BF and MIC to antifungals in Candida spp. isolates grown from urine samples of patients and performed a retrospective chart review to examine the correlation with risk factors. A total of 67 Candida spp. isolates were grown from urine samples from 55 patients. The species distribution was C. albicans (54%), C. glabrata (36%), and C. tropicalis (10%). BF varied greatly among individual Candida isolates but was stable in sequential isolates during chronic infection. BF also depended on the growth medium and especially in C. albicans was significantly enhanced in artificial urine (AU) compared to RPMI medium. In nine of the C. albicans strains BF was 4- to 10-fold higher in AU, whereas in three of the C. albicans strains and two of the C. glabrata strains higher BF was measured in RPMI medium than in AU. Determination of the MICs showed that planktonic cells of all strains were susceptible to amphotericin B (AMB) and caspofungin (CASPO) and that three of the C. glabrata strains and two of the C. albicans strains were resistant to fluconazole (FLU). In contrast, all biofilm-associated adherent cells were resistant to CASPO and FLU. The biofilms of 14 strains (28%) were sensitive to AMB (MIC₅₀ of <1 μg/ml). Correlation between degree of BF and MIC of AMB was not seen in RPMI grown biofilms but was present when grown in AU. A retrospective chart review demonstrated no correlation of known risk factors of candiduria with BF in AU or RPMI. We conclude that BF is a stable characteristic of Candida strains that varies greatly among clinical strains and is dependent on the growth medium. Resistance to AMB is associated with higher BF in AU, which may represent the more physiologic medium to test BF. Future studies should address whether in vitro BF can predict treatment failure in vivo.     

Citronellol disrupts membrane integrity by inducing free radical generation

Citronellol, an oxygenated monoterpene, is found naturally in the essential oils of several aromatic plants and has been reported to exhibit growth inhibitory and pesticidal activities. However, its mechanism of action is largely unexplored. We investigated the effect of citronellol, which is lipophilic in nature on membrane integrity in terms of lipid peroxidation, conjugated dienes content, membrane permeability, cell death, and activity of the enzyme lipoxygenase in roots of hydroponically grown wheat. Citronellol (50-250 microM) caused a significant inhibition of root and shoot growth. Furthermore, exposure to citronellol enhanced the solute leakage, increased the malondialdehyde content and lipoxygenase activity, and decreased the conjugated diene content. This indicates that citronellol induces generation of reactive oxygen species (ROS) resulting in lipid peroxidation and membrane damage. This was confirmed by in situ histochemical studies indicating cell death and disruption of membrane integrity. We conclude from this study that citronellol inhibits the root growth by ROS-mediated membrane disruption.