1,720,972 research outputs found
Cytofluorescence techniques for the visualization of distinct pools of protein thiols at the single cell level
No full text4-Hydroxynonenal (4-hydroxy-2,3-trans-nonenal; 4-HNE) is the best known and thoroughly studied aldehydic product originating in biological samples during the process of lipid peroxidation (Fig. 1) (1). The latter is an autocatalytic, self-propagating sequence of free radical reactions, ultimately resulting in the fragmentation of the carbon atom chains of unsaturated fatty acids esterified in phospholipids of cellular membranes, which can be set into motion in conditions of severe oxidative stress within the cell (2). Many of the lipid fragments thus originated are aldehydes and other carbonyl products, provided with variable reactivity towards cellular macro molecules. 4-HNE was originally identified in vitro as a specific, dialyzable, cytotoxic product of peroxidation of microsomal phospholipids (3), but subsequent studies have consistently detected it in a number of experimental conditions, in which it has been shown to exert a variety of biological actions (4), as well as in important human diseases such as atherosclerosis, neurodegeneration, and cancer (5–7) Like other α,β-unsaturated aldehydes, 4-HNE is capable of binding covalently to side chains of cysteine, histidine, lysine, and other amino acids in proteins (8), thus originating new epitopes that can be detected by suitable antibodies Fig. 2). Here a convenient procedure is described using polyclonal antibodies (PAbs) and fluorescent revelation
Modulation of human T-lymphocyte proliferation by 4-hydroxynonenal, the bioactive product of neutrophil-dependent lipid peroxidation
No full textThe proliferative capacity of immune cells is known to be sensitive to conditions of oxidative stress and lipid peroxidation. We tested the hypothesis that activated neutrophils can induce peroxidation in extracellular lipid substrates, and evaluated the effects of 4-hydroxy-2,3-trans-nonenal (4-HNE)--the most reactive aldehydic product of lipid peroxidation--on mitogen-induced proliferation of human T lymphocytes. Neutrophils activated in the presence of extracellular lipid substrates (liposomes, cellular membranes) induced lipid peroxidation. By means of cytoimmunofluorescent labeling and confocal microscopy, the binding of 4-HNE to surface and cytoplasmic proteins of activated neutrophils was observed. Short (20 min) pre-treatment of cells with low concentrations of 4-HNE were able to dose-dependently decrease the proliferation of human peripheral blood lymphocytes challenged with PHA or anti-CD3 monoclonal antibody OKT3, as well as the proliferation of a tetanus specific human T-cell line challenged with tetanus toxoid. In these conditions, the binding of 4-HNE to surface and cytoplasmic proteins of lymphocytes was also observed. When the proliferative capacity of peripheral blood lymphocytes was monitored over several days after 4-HNE treatment and PHA challenge, a recovery and a rebound in cell proliferation was observed. Data reported indicate that the lipid peroxidation promoted by activated neutrophils can exert modulatory effects on the responsivity of human T cells, through the action of its most reactive product, 4-HNE
Cell lineage-specific and developmental stage-specific controls of MHC class-II-antigen expression.
No full textIn this report we present evidence and we review data from our laboratory which indicate the genetic complexity of regulatory mechanisms controlling MHC class-II-gene expression. The MHC class-II genes can be expressed in 2 ways: in a constitutive fashion, as in B cells, and in an inducible fashion, as in macrophages, endothelial cells and certain tumors. In both cases the regulatory controls are mainly exerted at transcriptional level as a result of interactions between cis-acting regulatory DNA elements and trans-acting factors. The constitutive class-II-gene expression in B cells is under the control of developmentally regulated trans-acting factors with activator function and encoded by a series of genes, the AIR genes, one of which has been mapped in the mouse on chromosome 16. Interestingly, these regulatory mechanisms are conserved across species for at least 70 million years, because murine AIR-gene products can complement AIR gene defects of human B-cell mutants. The constitutive B-cell phenotype behaves as a dominant trait up to the plasma cell stage in which class-II-gene expression is lost because of the activation of suppressor factors which repress transcription and which, in turn, behave as a dominant trait in somatic cell hybrids between B cells and plasma cells. Thus positive and negative signals regulating class-II-gene expression may behave as dominant or recessive traits, depending upon the particular developmental stage of the cell in which they operate. The mechanisms controlling class-II expression in inducible cells are distinct from those mediating constitutive expression. Indeed, induction of these genes is not sufficient to complement AIR-gene defects in hybrids between macrophages and class-II-negative mutant B cells. In contrast, constitutive expression is dominant in hybrids between class-II-positive B cells and macrophages, suggesting that in uninduced cells class-II-gene activation does not take place more because of lack of activator factors than because of the presence of constitutive transcriptional suppressors. On the basis of these results, we propose a model for developmentally controlled MHC class-II-gene expression during ontogeny
Determination of a redox compensation index and its relationships to glycaemic control in type 2 diabetes mellitus
No full textKinetic immunodominance: functionally competing antibodies against exposed and cryptic epitopes of Escherichia coli beta-galactosidase are produced in time sequence.
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Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Differential activation of T cell clones stimulated by macrophages exposed to antigen complexed with monoclonal antibodies. A possible influence of paratope specificity on the mode of antigen processing.
No full textThe Air-1 locus controlling constitutive expression of MHC class II genes is developmentally active in B cells and silent in macrophages
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