Dengue-2 and yellow fever 17DD viruses infect human dendritic cells, resulting in an induction of activation markers, cytokines and chemokines and secretion of different TNF-α and IFN-α profiles

Flaviviruses cause severe acute febrile and haemorrhagic infections, including dengue and yellow fever and the pathogenesis of these infections is caused by an exacerbated immune response. Dendritic cells (DCs) are targets for dengue virus (DENV) and yellow fever virus (YF) replication and are the first cell population to interact with these viruses during a natural infection, which leads to an induction of protective immunity in humans. We studied the infectivity of DENV2 (strain 16681), a YF vaccine (YF17DD) and a chimeric YF17D/DENV2 vaccine in monocyte-derived DCs in vitro with regard to cell maturation, activation and cytokine production. Higher viral antigen positive cell frequencies were observed for DENV2 when compared with both vaccine viruses. Flavivirus-infected cultures exhibited dendritic cell activation and maturation molecules. CD38 expression on DCs was enhanced for both DENV2 and YF17DD, whereas OX40L expression was decreased as compared to mock-stimulated cells, suggesting that a T helper 1 profile is favoured. Tumor necrosis factor (TNF)-α production in cell cultures was significantly higher in DENV2-infected cultures than in cultures infected with YF17DD or YF17D/DENV. In contrast, the vaccines induced higher IFN-α levels than DENV2. The differential cytokine production indicates that DENV2 results in TNF induction, which discriminates it from vaccine viruses that preferentially stimulate interferon expression. These differential response profiles may influence the pathogenic infection outcome

Multiple actin binding domains of Ena/VASP proteins determine actin network stiffening

Vasodilator-stimulated phosphoprotein (Ena/ VASP) is an actin binding protein, important for actin dynamics in motile cells and developing organisms. Though VASP's main activity is the promotion of barbed end growth, it has an F-actin binding site and can form tetramers, and so could additionally play a role in actin crosslinking and bundling in the cell. To test this activity, we performed rheology of reconstituted actin networks in the presence of wild-type VASP or mutants lacking the ability to tetramerize or to bind G-actin and/or F-actin. We show that increasing amounts of wild-type VASP increase network stiffness up to a certain point, beyond which stiffness actually decreases with increasing VASP concentration. The maximum stiffness is 10-fold higher than for pure actin networks. Confocal microscopy shows that VASP forms clustered actin filament bundles, explaining the reduction in network elasticity at high VASP concentration. Removal of the tetramerization site results in significantly reduced bundling and bundle clustering, indicating that VASP's flexible tetrameric structure causes clustering. Removing either the F-actin or the G-actin binding site diminishes VASP's effect on elasticity, but does not eliminate it. Mutating the F-actin and G-actin binding site together, or mutating the F-actin binding site and saturating the G-actin binding site with monomeric actin, eliminates VASP's ability to increase network stiffness. We propose that, in the cell, VASP crosslinking confers only moderate increases in linear network elasticity, and unlike other crosslinkers, VASP's network stiffening activity may be tuned by the local concentration of monomeric actin. © European Biophysical Societies' Association 2012

Density Functional Theory for Magnetism and Magnetic Anisotropy

Density functional theory and its application for the simulation of magnetic properties of condensed matter is introduced. This includes vector-spin density functional theory for the evaluation of spin-spin interactions and relativistic extensions to capture effects like the magnetocrystalline anisotropy. The role of the different approximations to the exchange-correlation functional, e.g., the local density approximation, or the generalized gradient approximation, is investigated, showing successes and limitations of the present functionals. Special techniques to determine, e.g., the magnetic ground state or finite temperature properties based on density functional theory are shortly discussed

Carbohydrate secondary and tertiary structure using raman spectroscopy

Raman spectroscopy is a long-established analytical technique that has now proliferated into a variety of research tools that are able to identify and characterize almost any type of molecule under most conditions. As such, Raman spectroscopies are well suited to the study of carbohydrates, from simple monosaccharides to the largest glycosaminoglycans and from industrial bioreactors to in situ measurements on living cells. This review covers a range of examples of how Raman techniques are addressing the questions of glycobiologists working on diverse aspects of this fascinating but poorly understood class of biomolecules. Focus is placed on the application of Raman, surface-enhanced Raman, Raman optical activity, and related spectroscopies to characterizing carbohydrates of all types, with only a general introduction to the theory of the techniques themselves. Particular attention is also paid to the computational tools now regularly used by spectroscopists to analyze complex data. Although this review is aimed at the glycobiology community, the examples discussed also demonstrate to the expert spectroscopist how their techniques can impact on the exciting opportunities presented by working with carbohydrates

Molecular insights into transgenerational non-genetic inheritance of acquired behaviours

Behavioural traits in mammals are influenced by environmental factors, which can interact with the genome and modulate its activity by complex molecular interplay. Environmental experiences can modify social, emotional and cognitive behaviours during an individual's lifetime, and result in acquired behavioural traits that can be transmitted to subsequent generations. This Review discusses the concept of, and experimental support for, non-genetic transgenerational inheritance of acquired traits involving the germ line in mammals. Possible mechanisms of induction and maintenance during development and adulthood are considered along with an interpretation of recent findings showing the involvement of epigenetic modifications and non-coding RNAs in male germ cells