Anodic alumina films formed in sulfamic acid solution

The formation of anodic oxide films on aluminium in 5% aqueous solution of sulfamic acid is investigated. The investigations were carried out in galvanostatic conditions and at different temperatures and durations. The porosity of porous alumina samples grown under different conditions is determined by the pore-filling method and scanning electron microscopy. The effect of the current density, temperature and duration of the anodic oxidation on the morphology of the porous Al₂O₃-films is studied.     

Common conformational changes induced in type 2 picornavirus IRESs by cognate trans-acting factors

Type 2 internal ribosomal entry sites (IRESs) of encephalomyocarditis virus (EMCV), foot-and-mouth disease virus (FMDV) and other picornaviruses comprise five major domains H-L. Initiation of translation on these IRESs begins with specific binding of the central domain of initiation factor, eIF4G to the J-K domains, which is stimulated by eIF4A. eIF4G/eIF4A then restructure the region of ribosomal attachment on the IRES and promote recruitment of ribosomal 43S pre-initiation complexes. In addition to canonical translation factors, type 2 IRESs also require IRES trans-acting factors (ITAFs) that are hypothesized to stabilize the optimal IRES conformation that supports efficient ribosomal recruitment: the EMCV IRES is stimulated by pyrimidine tract binding protein (PTB), whereas the FMDV IRES requires PTB and ITAF(45). To test this hypothesis, we assessed the effect of ITAFs on the conformations of EMCV and FMDV IRESs by comparing their influence on hydroxyl radical cleavage of these IRESs from the central domain of eIF4G. The observed changes in cleavage patterns suggest that cognate ITAFs promote similar conformational changes that are consistent with adoption by the IRESs of comparable, more compact structures, in which domain J undergoes local conformational changes and is brought into closer proximity to the base of domain I.     

Psychiatric classifications: validity and utility

Despite historical assumptions to the contrary, there is little evidence that the majority of recognized mental disorders are separated by natural boundaries. Diagnostic categories defined by their clinical syndromes should be regarded as ‘valid’ only if they have been shown to be truly discrete entities. Most diagnostic concepts in psychiatry have not been demonstrated to be valid in this sense, though many possess ‘utility’ by virtue of the information they convey about presenting symptoms, outcome, treatment response and, in some instances, aetiology. While researchers in genetics, neurobiology and population epidemiology are increasingly more likely to adopt a continuum/dimensional view of the variation in symptomatology, clinicians prefer to hold on to the categorical approach embodied in current classifications such as ICD‐10 and DSM‐5. Both points of view have plausible justification in their respective contexts, but the way forward may be in their conceptual reconciliation.     

Structure and membrane interaction of the internal fusion peptide of avian sarcoma leukosis virus.

The structure and membrane interaction of the internal fusion peptide (IFP) fragment of the avian sarcoma and leucosis virus (ASLV) envelope glycoprotein was studied by an array of biophysical methods. The peptide was found to induce lipid mixing of vesicles more strongly than the fusion peptide derived from the N-terminal fusion peptide of influenza virus (HA2-FP). It was observed that the helical structure was enhanced in association with the model membranes, particularly in the N-terminal portion of the peptide. According to the infrared study, the peptide inserted into the membrane in an oblique orientation, but less deeply than the influenza HA2-FP. Analysis of NMR data in sodium dodecyl sulfate micelle suspension revealed that Pro13 of the peptide was located near the micelle-water interface. A type II beta-turn was deduced from NMR data for the peptide in aqueous medium, demonstrating a conformational flexibility of the IFP in analogy to the N-terminal FP such as that of gp41. A loose and multimodal self-assembly was deduced from the rhodamine fluorescence self-quenching experiments for the peptide bound to the membrane bilayer. Oligomerization of the peptide and its variants can also be observed in the electrophoretic experiments, suggesting a property in common with other N-terminal FP of class I fusion proteins.     

Characterization of mesenchymal stem cells isolated from the human umbilical cord

Numerous papers have reported that mesenchymal stem cells (MSCs) can be isolated from various sources such as bone marrow, adipose tissue and others. Nonetheless it is an open question whether MSCs isolated from different sources represent a single cell lineage or if cells residing in different organs are separate members of a family of MSCs. Subendothelial tissue of the umbilical cord vein has been shown to be a promising source of MSCs. The aim of this study was to isolate and characterize cells derived from the subendothelial layer of umbilical cord veins as regards their clonogenicity and differentiation potential. The results from these experiments show that cells isolated from the umbilical cord vein displayed fibroblast-like morphology and grew into colonies. Immunophenotyping by flow cytometry revealed that the isolated cells were negative for the hematopoietic line markers HLA-DR and CD34 but were positive for CD29, CD90 and CD73. The isolated cells were also positive for survivin, Bcl-2, vimentin and endoglin, as confirmed by RT-PCR and immunofluorescence. These cells can be induced to differentiate into osteogenic and adipogenic cells, but a new finding is that these cells can be induced to differentiate into endothelial cells expressing CD31, vWF and KDR-2, and also form vessel-like structures in Matrigel. The differentiated cells stopped expressing survivin, thus showing a diminished proliferative potential. It can be assumed that the subendothelial layer of the umbilical cord vein contains a population of cells with the overall characteristics of MSCs, with the additional capability to transform into endothelial cells.     

Secondary structure, phospholipid membrane interactions, and fusion activity of two glutamate-rich analogs of influenza hemagglutinin fusion peptide

Two synthetic mutants of influenza HA2 fusion peptide (residues 1-25), containing Glu on the polar (residues 4,8-E5(4,8)) or the hydrophobic (residues 3,7-E5(3,7)) face of the amphipathic helix, were synthesized and labeled with NBD at the N-terminus. Introduction of Glu residues into the fusion peptide leads to increased sensitivity of various biochemical properties to pH compared to the wild type. The E5 peptides showed a decrease of alpha-helix content and increase of beta-sheet structure. Lipid binding was diminished, but not abolished even at high pH. The E5 analogs penetrate the lipid bilayer less deeply than the wild type, especially at high pH. The N-terminal half of the peptide showed significant variation of the depth of the penetration into the lipid bilayer. Both E5 peptides were fusion active. The properties of E5(3,7) were more affected by the Glu substitution and showed greater variation with pH than E5(4,8).     

Deleterious GRM1 mutations in schizophrenia

We analysed a phenotypically well-characterised sample of 450 schziophrenia patients and 605 controls for rare non-synonymous single nucleotide polymorphisms (nsSNPs) in the GRM1 gene, their functional effects and family segregation. GRM1 encodes the metabotropic glutamate receptor 1 (mGluR1), whose documented role as a modulator of neuronal signalling and synaptic plasticity makes it a plausible schizophrenia candidate. In a recent study, this gene was shown to harbour a cluster of deleterious nsSNPs within a functionally important domain of the receptor, in patients with schizophrenia and bipolar disorder. Our Sanger sequencing of the GRM1 coding regions detected equal numbers of nsSNPs in cases and controls, however the two groups differed in terms of the potential effects of the variants on receptor function: 6/6 case-specific and only 1/6 control-specific nsSNPs were predicted to be deleterious. Our in-vitro experimental follow-up of the case-specific mutants showed that 4/6 led to significantly reduced inositol phosphate production, indicating impaired function of the major mGluR1 signalling pathway; 1/6 had reduced cell membrane expression; inconclusive results were obtained in 1/6. Family segregation analysis indicated that these deleterious nsSNPs were inherited. Interestingly, four of the families were affected by multiple neuropsychiatric conditions, not limited to schizophrenia, and the mutations were detected in relatives with schizophrenia, depression and anxiety, drug and alcohol dependence, and epilepsy. Our findings suggest a possible mGluR1 contribution to diverse psychiatric conditions, supporting the modulatory role of the receptor in such conditions as proposed previously on the basis of in vitro experiments and animal studies.     

Hho1p,the linker histone of Saccharomyces cerevisiae, is important for the proper chromatin organization in vivo

Despite the existence of certain differences between yeast and higher eukaryotic cells a considerable part of our knowledge on chromatin structure and function has been obtained by experimenting on Saccharomyces cerevisiae. One of the peculiarities of S. cerevisiae cells is the unusual and less abundant linker histone, Hho1p. Sparse is the information about Hho1p involvement in yeast higher-order chromatin organization. In an attempt to search for possible effects of Hho1p on the global organization of chromatin, we have applied Chromatin Comet Assay (ChCA) on HHO1 knock-out yeast cells. The results showed that the mutant cells exhibited highly distorted higher-order chromatin organization. Characteristically, linker histone depleted chromatin generally exhibited longer chromatin loops than the wild-type. According to the Atomic force microscopy data the wild-type chromatin appeared well organized in structures resembling quite a lot the “30-nm” fiber in contrast to HHO1 knock-out yeast.     

Dendritic cell actin dynamics control contact duration and priming efficiency at the immunological synapse

Dendritic cells (DCs) are crucial for the priming of naive T cells and the initiation of adaptive immunity. Priming is initiated at a heterologous cell–cell contact, the immunological synapse (IS). While it is established that F-actin dynamics regulates signaling at the T cell side of the contact, little is known about the cytoskeletal contribution on the DC side. Here, we show that the DC actin cytoskeleton is decisive for the formation of a multifocal synaptic structure, which correlates with T cell priming efficiency. DC actin at the IS appears in transient foci that are dynamized by the WAVE regulatory complex (WRC). The absence of the WRC in DCs leads to stabilized contacts with T cells, caused by an increase in ICAM1-integrin–mediated cell–cell adhesion. This results in lower numbers of activated and proliferating T cells, demonstrating an important role for DC actin in the regulation of immune synapse functionality.