Effect of urban sewage treatment on total and methyl mercury concentrations in effluents

The purpose of this study was to investigate the effect of sewage treatment on total mercury (THg) and methylmercury (MeHg) concentrations in domestic effluents and the contribution of urban sewage treatment facilities to THg and MeHg in rivers. We determined the concentrations of THg and MeHg in unfiltered samples of untreated and treated domestic sewage from the three treatment facilities and receiving river water within the City of Winnipeg. The concentrations of THg in the Red and Assiniboine rivers ranged from 3–31 ng/L. THg was related positively to suspended sediment concentrations in the rivers. The concentrations of MeHg in these rivers were usually 0.2–0.3 ng/L. THg concentrations in raw sewage varied widely, from 2–150 ng/L. Treatment removed an average of 88% of this mercury. MeHg concentrations in raw sewage were 0.5–4.3 ng/L, however, after treatment at two treatment facilities, MeHg was greatly reduced, usually to 0.1–0.4 ng/L. Most treated sewage, therefore, had MeHg concentrations that were similar to levels in the receiving rivers and the effect of discharged effluent was usually a change of about 2% or less on concentrations in the rivers. However, one of the facilities (the West End plant) was discharging higher concentrations of MeHg, up to 2 ng/L, causing calculated increases of up to 11% in the concentration of MeHg in the Assiniboine River.     

Infectious Chikungunya Virus in the Saliva of Mice,Monkeys and Humans

Chikungunya virus (CHIKV) is a reemerging, ordinarily mosquito-transmitted, alphavirus that occasionally produces hemorrhagic manifestations, such as nose bleed and bleeding gums, in human patients. Interferon response factor 3 and 7 deficient (IRF3/7^-/-) mice, which are deficient for interferon α/β responses, reliably develop hemorrhagic manifestations after CHIKV infection. Here we show that infectious virus was present in the oral cavity of CHIKV infected IRF3/7^-/- mice, likely due to hemorrhagic lesions in the olfactory epithelium that allow egress of infected blood into the nasal, and subsequently, oral cavities. In addition, IRF3/7^-/- mice were more susceptible to infection with CHIKV via intranasal and oral routes, with IRF3/7^-/- mice also able to transmit virus mouse-to-mouse without an arthropod vector. Cynomolgus macaques often show bleeding gums after CHIKV infection, and analysis of saliva from several infected monkeys also revealed the presence of viral RNA and infectious virus. Furthermore, saliva samples collected from several acute CHIKV patients with hemorrhagic manifestations were found to contain viral RNA and infectious virus. Oral fluids can therefore be infectious during acute CHIKV infections, likely due to hemorrhagic manifestations in the oral/nasal cavities.     

Surface features of the lipid droplet mediate perilipin 2 localization

All eukaryotic organisms store excess lipid in intracellular lipid droplets. These dynamic structures are associated with and regulated by numerous proteins. Perilipin 2, an abundant protein on most lipid droplets, promotes neutral lipid accumulation in lipid droplets. However, the mechanism by which perilipin 2 binds to and remains anchored on the lipid droplet surface is unknown. Here we identify features of the lipid droplet surface that influence perilipin 2 localization. We show that perilipin 2 binding to the lipid droplet surface requires both hydrophobic and electrostatic interactions. Reagents that disrupt these interactions also decrease binding. Moreover, perilipin 2 binding does not depend on other lipid droplet-associated proteins but is influenced by the lipid composition of the surface. Perilipin 2 binds to synthetic vesicles composed of dioleoylphosphatidylcholine, a phospholipid with unsaturated acyl chains. Decreasing the temperature of the binding reaction, or introducing phospholipids with saturated acyl chains, decreases binding. We therefore demonstrate a role for surface lipids and acyl chain packing in perilipin 2 binding to lipid droplets. The ability of the lipid droplet phospholipid composition to impact protein binding may link changes in nutrient availability to lipid droplet homeostasis.     

Randomly organized lipids and marginally stable proteins: A coupling of weak interactions to optimize membrane signaling

Eukaryotic lipids in a bilayer are dominated by weak cooperative interactions. These interactions impart highly dynamic and pliable properties to the membrane. C2 domain-containing proteins in the membrane also interact weakly and cooperatively giving rise to a high degree of conformational plasticity. We propose that this feature of weak energetics and plasticity shared by lipids and C2 domain-containing proteins enhance a cell's ability to transduce information across the membrane. We explored this hypothesis using information theory to assess the information storage capacity of model and mast cell membranes, as well as differential scanning calorimetry, carboxyfluorescein release assays, and tryptophan fluorescence to assess protein and membrane stability. The distribution of lipids in mast cell membranes encoded 5.6–5.8 bits of information. More information resided in the acyl chains than the head groups and in the inner leaflet of the plasma membrane than the outer leaflet. When the lipid composition and information content of model membranes were varied, the associated C2 domains underwent large changes in stability and denaturation profile. The C2 domain-containing proteins are therefore acutely sensitive to the composition and information content of their associated lipids. Together, these findings suggest that the maximum flow of signaling information through the membrane and into the cell is optimized by the cooperation of near-random distributions of membrane lipids and proteins. This article is part of a Special Issue entitled: Interfacially Active Peptides and Proteins. Guest Editors: William C. Wimley and Kalina Hristova.     

The coconut palm,Cocos nucifera,impacts forest composition and soil characteristics at Palmyra Atoll,Central Pacific

Question: Cocos nucifera, the coconut palm, has a pantropical distribution and reaches near monodominance in many atolls, low lying islands and coastal regions. This paper examines the ecological correlation between C. nucifera abundance and changes in forest structure, floristic diversity and forest soil characteristics. Location: Palmyra Atoll NWR (USA), Central Pacific Ocean. Methods: Plant surveys were conducted on 83 transects (each 100 m²). All plants ≥5 cm in height were identified and counted; large plants were also measured and ground cover was surveyed. Major macronutrients, pH, macro‐elements/base cations, micronutrients and pedogenic elements, and thermodynamic stability levels were quantified from soil samples taken at each transect. Results: Even in a low diversity atoll environment, we found that high abundances of C. nucifera corresponded with pronounced differences in forest communities including: lower diversity of established trees and regenerating understorey; higher stem density and stand basal area; lower abundance of major macronutrients; and differences in macro and trace elements and energy content of soil organic matter. Historical natural experiments document that the expansion of C. nucifera was the likely causative agent of these changes. Discussion: Cumulatively, these data show that C. nucifera has important impacts on floristic, structural and soil characteristics of forests where it becomes dominant. Given the high proportion of tropical coastal areas in which C. nucifera is now naturalized and abundant, this likely has important implications for coastal forest diversity and structure.     

The N-glycosylation of classical swine fever virus E2 glycoprotein extracellular domain expressed in the milk of goat

Classical swine fever virus (CSFV) outer surface E2 glycoprotein represents an important target to induce protective immunization during infection but the influence of N-glycosylation pattern in antigenicity is yet unclear. In the present work, the N-glycosylation of the E2-CSFV extracellular domain expressed in goat milk was determined. Enzymatic N-glycans releasing, 2-aminobenzamide (2AB) labeling, weak anion-exchange and normal-phase HPLC combined with exoglycosidase digestions and mass spectrometry of 2AB-labeled and unlabeled N-glycans showed a heterogenic population of oligomannoside, hybrid and complex-type structures. The detection of two Man₈GlcNAc₂ isomers indicates an alternative active pathway in addition to the classical endoplasmic reticulum processing. N-acetyl or N-glycolyl monosialylated species predominate over neutral complex-type N-glycans. Asn207 site-specific micro-heterogeneity of the E2 most relevant antigenic and virulence site was determined by HPLC-mass spectrometry of glycopeptides. The differences in N-glycosylation with respect to the native E2 may not disturb the main antigenic domains when expressed in goat milk.     

Inhibition of mammalian glycan biosynthesis produces non-self antigens for a broadly neutralising, HIV-1 specific antibody

The HIV envelope has evolved a dense array of immunologically "self" carbohydrates that efficiently protect the virus from antibody recognition. Nonetheless, one broadly neutralising antibody, IgG1 2G12, has been shown to recognise a cluster of oligomannose glycans on the HIV-1 surface antigen gp120. Thus the self carbohydrates of HIV are now regarded as potential targets for viral neutralisation and vaccine design. Here, we show that chemical inhibition of mammalian glycoprotein synthesis, with the plant alkaloid kifunensine, creates multiple HIV (2G12) epitopes on the surface of previously non-antigenic self proteins and cells, including HIV gp120. This formally demonstrates the structural basis for self/non-self discrimination between viral and host glycans, by a neutralising antibody. Moreover, this study provides an alternative protein engineering approach to the design of a carbohydrate vaccine for HIV-1 by chemical synthesis.     

Functional defects of SKAP-55-deficient T cells identify a regulatory role for the adaptor in LFA-1 adhesion

The ADAP-SKAP-55 module regulates T-cell receptor (TCR)-induced integrin clustering and adhesion in T cells. However, it has been unclear whether ADAP and/or SKAP-55 is an effector of the response. ADAP controls SKAP-55 expression such that ADAP(-/-) T cells are also deficient in SKAP-55 expression. In this study, we report the phenotype of the SKAP-55-deficient mouse. SKAP-55(-/-) T cells retain ADAP expression yet show defects in beta1 and beta2 integrin adhesion, leukocyte function-associated antigen 1 (LFA-1) clustering, production of the cytokines interleukin-2 and gamma interferon, and proliferation. This dependency was also reflected in more-transient conjugation times in response to the superantigen staphylococcal enterotoxin A on dendritic cells and a reduced number of cells with TCR/CD3 microcluster localization at the immunological synapse. SKAP-55(-/-) T cells showed the same general impairment of function as ADAP(-/-) T cells, indicating that SKAP-55 is an effector of the ADAP-SKAP-55 module. At the same time, the requirement for ADAP and SKAP-55 was not absolute, since a subset of peripheral T cells adhered with loss of expression of either adaptor. Further, dependency on SKAP-55 or ADAP differed with the strength of the TCR signal. As with the ADAP(-/-) mouse, SKAP-55-deficient mice showed no major effects on lymphoid development or the appearance of peripheral T cells, B cells, and NK cells. Our findings identify a clear effector role for SKAP-55 in LFA-1 adhesion in peripheral T cells and demonstrate that dependency on SKAP-55 and ADAP differs among T cells and differs with the strength of the TCR signal.