Dynamic Analyses of Lymphoblast Membranes Exposed to Alpha Interferon Using Flow Cytometry and Fluorescence Recovery after Photobleaching

Interferons represent a major group of the biologic response modifiers which exert multipotent effects upon cell growth, cytodifferentiation and immune functions. Previous experimental studies with alpha interferon (IFN-) have suggested that modulation of transmembrane signaling could be a critical determinant in the bioregulatory diversity. To determine whether any initial changes at the plasma membrane would directly correlate with one or more actions of IFN-, we investigated cultures of Daudi lymphoblasts which are uniquely susceptible to growth inhibition. Complementary biophysical techniques were applied. In one approach, changes in plasma membrane ion flux were measured by flow cytometry, using a fluorescent dye indicator of membrane potential: Cells briefly exposed (5-10 min) to a DNA-recombinant IFN-2 (100 to 800 U/ml) manifested a consistent plasma membrane hyperpolarization (—60 to —90 mV) which could be blocked by ouabain. In a second approach, changes in diffusion coefficients of plasma membrane-associated macromolecules were determined by measuring the fluorescence redistribution after pulse photobleaching (FRAP): Individual plasma membrane proteins (sIgM, Leu 12 or Leu 16) were la-belled with FITC conjugated goat antibodies [F(ab\u27)2 or Fab\u27] or with phycoerythrin-B conjugated monoclonal mouse anti-bodies. Statistical comparisons of cells exposed to IFN-a2 for 10 to 30 min showed immediate 27 to 88 % increases in mean lateral diffusion rates. Mutant Daudi cells, cloned for resistance to growth inhibition showed no plasma membrane hyperpolarization with IFN-2 (up to 1000 U/ ml), and baseline lateral diffusion coefficients matched those ofIFN-2-treated, non-resistant cells. We conclude that biophysical status and responses of the plasma membrane must be closely linked to the molecular mechanisms of anti-proliferative signal transduction

Towards a microscopic description of dimer adsorbates on metallic surfaces

Despite the experimental successes of Scanning Tunneling Microscopy (STM) and the interest in more complex magnetic nanostructures, our present understanding and theoretical description of STM spectra of magnetic adatoms is mainly phenomenological and most often ignores many-body effects. Here, we propose a theory which includes a microscopic description of the wave functions of the substrate and magnetic adatoms together with quantum many-body effects. To test our theory, we have computed the STM spectra of magnetic Cobalt monomers and dimers adsorbed on metallic Copper surfaces and succesfully compared our results to recent available experimental data.Comment: 4 pages, 2 figures, discussion of calculation of RKKY interaction and connection to NRG included. Extended discussion on calculations of the one-electron parameters of Anderson model. Typos correcte

Double layer in ionic liquids: Overscreening vs. crowding

We develop a simple Landau-Ginzburg-type continuum theory of solvent-free ionic liquids and use it to predict the structure of the electrical double layer. The model captures overscreening from short-range correlations, dominant at small voltages, and steric constraints of finite ion sizes, which prevail at large voltages. Increasing the voltage gradually suppresses overscreening in favor of the crowding of counterions in a condensed inner layer near the electrode. The predicted ion profiles and capacitance-voltage relations are consistent with recent computer simulations and experiments on room-temperature ionic liquids, using a correlation length of order the ion size.Comment: 4 pages + supplementary informatio

Tubuloreticular Reorganization of Cytomembranes in Cells Treated with with Human Alpha Interferons - A Review

Human alpha interferons (IFN-a) cause a reorganization of internal cell membranes into tubuloreticular inclusions (TRI). Morphogenesis and cytochemistry indicate a pre-Golgi intracisternal origin from the endoplasmic reticulum. Clinically, TRI formation in human blood mononuclear cells correlates with systemic IFN-a treatment or with endogenous overproduction of IFN-a in viral or autoimmune diseases (e.g., rubella syndrome, AIDS, systemic lupus erythematosus). In vitro, TRI formation can be produced by treatment of Daudi lymphoblasts or vascular endothelial cells with IFN-a, and is blocked by actinomycin-D. In Daudi lymphoblasts or vascular endothelial cell cultures, TRI formation parallels induction of 2\u27-5\u27 A synthetase, inhibition of thymidine kinase and growth inhibition; however, heavy water treatment of Daudi cells prevented TRI formation while induction of 2\u27-5\u27 A synthetase and growth inhibition persisted. TRI formation was dissociated from IFN-a antiproliferative activity in a mutant clone of Daudi lymphoblasts. Decreased glycoprotein biosynthesis and increased phospholipid biosynthesis may accompany progressive TRI accumulation

Phase transitions in two-dimensional anisotropic quantum magnets

We consider quantum Heisenberg ferro- and antiferromagnets on the square lattice with exchange anisotropy of easy-plane or easy-axis type. The thermodynamics and the critical behaviour of the models are studied by the pure-quantum self-consistent harmonic approximation, in order to evaluate the spin and anisotropy dependence of the critical temperatures. Results for thermodynamic quantities are reported and comparison with experimental and numerical simulation data is made. The obtained results allow us to draw a general picture of the subject and, in particular, to estimate the value of the critical temperature for any model belonging to the considered class.Comment: To be published on Eur. Phys. J.

A simple technique for flat osmicating and flat embedding of immunolabelled vibratome sections of the rat spinal cord for light and electron microscopy

We describe here a simple technique for flat-osmicating and flat-embedding of immunolabelled vibratome sections. The technique is particularly useful for large specimens such as whole cross-sections of rat spinal cord. After the vibratome section has been flat-osmicated on a flat surface under a glass cover slip, it is dehydrated and then embedded by placing it in a small drop of epoxy resin on a flat base of polypropylene plastic and overlaying a small square piece of cellulose acetate cut from heat-resistant overhead projector transparency film for photocopying. The thin layer of resin containing the flat-embedded vibratome section is then separated from the base and glued onto the flat end of a pre-polymerised blank block of resin. The method produces flat-embedded vibratome sections and thus allows serial large uniformly labelled semithin and ultrathin sections to be obtained of the whole cross-section of the rat spinal cord. This facilitates the observation and quantification of labelled cells in the specimen. Because of its simplicity the technique also allows one worker to process more than 100 vibratome sections at the one time

Complexities of atomic structure at CdO/MgO and CdO/Al2O3 interfaces

We report the interface structures of CdO thin films on (001)-MgO and (0001)-Al2O3 substrates. Using aberration corrected scanning transmission electron microscopy, we show that epitaxial growth of (001)-CdO∥(001)-MgO occurs with a lattice misfit greater than 10%. A high density of interface misfit dislocations is found to form. In combination with molecular dynamics simulations, we show that dislocation strain fields form and overlap in very thin heterostructures of CdO and MgO (<3 nm). On the c-Al2O3 substrate, we find that CdO grows with a surface normal of [025]. We show that three rotation variants form due to the symmetry of the sapphire surface. These results contribute insights into the epitaxial growth of these rock-salt oxides

Relationships of Stigma and Shame to Gonorrhea and HIV Screening

Objectives. The purpose of this study was to assess the relationships between stigma and shame associated with seeking treatment for sexually transmitted diseases (STDs) and undergoing testing for gonorrhea and HIV. Methods. Participants were 847 males and 1126 females (mean age: 24.9 years) in 7 cities. Two scales assessed STD-related stigma and STD-related shame. Results. Rates of stigma and shame were higher among participants without a gonorrhea test in the past year and among those without an HIV test. Sex, age, health service use, previous suspicion of gonorrhea, and low levels of stigma were independently associated with gonorrhea testing. Age, enrollment site, use of health services, gonorrhea testing, and low levels of stigma were independently associated with HIV testing. Conclusions. Shame is part of the experience of seeking STD-related care, but stigma may be a more powerful barrier to obtaining such care