1,151 research outputs found
Conformational epitopes of myelin oligodendrocyte glycoprotein are targets of potentially pathogenic antibody responses in multiple sclerosis
<p>Abstract</p> <p>Background</p> <p>Myelin/oligodendrocyte glycoprotein (MOG) is a putative autoantigen in multiple sclerosis (MS). Establishing the pathological relevance and validity of anti-MOG antibodies as biomarkers has yielded conflicting reports mainly due to different MOG isoforms used in different studies. Because epitope specificity may be a key factor determining anti-MOG reactivity we aimed at identifying <it>a priori </it>immunodominant MOG epitopes by monoclonal antibodies (mAbs) and at assessing clinical relevance of these epitopes in MS.</p> <p>Methods</p> <p>Sera of 325 MS patients, 69 patients with clinically isolated syndrome and 164 healthy controls were assayed by quantitative, high-throughput ELISA for reactivity to 3 different MOG isoforms, and quantitative titers correlated with clinical characteristics. mAbs defined unique immunodominant epitopes distinct to each of the isoforms.</p> <p>Results</p> <p>In the majority of human samples anti-MOG levels were skewed towards low titers. However, in 8.2% of samples high-titer anti-MOG antibodies were identified. In contrast to anti-MOG reactivity observed in a mouse model of MS, in patients with MS these never reacted with ubiquitously exposed epitopes. Moreover, in patients with relapsing-remitting MS high-titer anti-MOG IgG correlated with disability (EDSS; Spearman r = 0.574; p = 0.025).</p> <p>Conclusions</p> <p>Thus high-titer reactivity likely represents high-affinity antibodies against pathologically relevant MOG epitopes, that are only present in a small proportion of patients with MS. Our study provides valuable information about requirements of anti-MOG reactivity for being regarded as a prognostic biomarker in a subtype of MS.</p
Detection of sperm antigens on mouse ova and early embryos
Serum and colostrum antibodies against mouse sperm were developed in two rabbits after systemic and mammary gland immunizations. Indirect immunofluorescence utilizing fluorescein-labeled goat antisera against rabbit IgG and IgA, respectively, indicated that both immune serum (IS) and colostrum (IC) compared with control samples caused intensive staining of the acrosome and tail of sperm. Absorption of IS and IC with mouse serum and the spleen, kidney, liver, and brain of male mice did not reduce the strength or the pattern of staining reaction on sperm. The absorbed IS reacted with cell surfaces of oocytes, unfertilized ova, zygotes, two-cell and four- to eight-cell fertilized ova, and blastocysts. The absorbed IC, however, reacted only with the four- to eight-cell embryo and blastocyst. Further absorption of the IS with mouse ovary removed the reaction with unfertilized ova and the one- to two-cell fertilized ova, but the staining of later embryo stages was unaffected. Therefore, it appears that specific rabbit anti-sperm antibodies are detecting two cell-membrane antigens on mouse embryos: one originating from the ovary and the other arising after fertilization.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/22638/1/0000189.pd
Exact Critical Exponents for Pseudo-Particles in the Kondo Problem
Exact critical exponents of the Green functions for pseudo-fermions and slave
bosons in the SU() Anderson model with are obtained by
using the Bethe ansatz solution and boundary conformal field theory. They are
evaluated exactly for mixed valence systems and Kondo systems with crystalline
fields. The results agree with the prediction of Menge and M\"uller-Hartmann,
which coincide with those of the X-ray problem. Some implication of our results
in one-dimensional chiral systems is also discussed.Comment: 9 pages, no figure
Evidence for Contemporary Switching of the O-Antigen Gene Cluster between Shiga Toxin-Producing Escherichia coli Strains Colonizing Cattle
Shiga toxin-producing Escherichia coli (STEC) comprise a group of zoonotic enteric pathogens with ruminants, especially cattle, as the main reservoir. O-antigens are instrumental for host colonization and bacterial niche adaptation. They are highly immunogenic and, therefore, targeted by the adaptive immune system. The O-antigen is one of the most diverse bacterial cell constituents and variation not only exists between different bacterial species, but also between individual isolates/strains within a single species. We recently identified STEC persistently infecting cattle and belonging to the different serotypes O156:H25 (n = 21) and O182:H25 (n = 15) that were of the MLST sequence types ST300 or ST688. These STs differ by a single nucleotide in purA only. Fitness-, virulence-associated genome regions, and CRISPR/CAS (clustered regularly interspaced short palindromic repeats/CRISPR associated sequence) arrays of these STEC O156:H25 and O182:H25 isolates were highly similar, and identical genomic integration sites for the stx converting bacteriophages and the core LEE, identical Shiga toxin converting bacteriophage genes for stx1a, identical complete LEE loci, and identical sets of chemotaxis and flagellar genes were identified. In contrast to this genomic similarity, the nucleotide sequences of the O-antigen gene cluster (O-AGC) regions between galF and gnd and very few flanking genes differed fundamentally and were specific for the respective serotype. Sporadic aEPEC O156:H8 isolates (n = 5) were isolated in temporal and spatial proximity. While the O-AGC and the corresponding 5′ and 3′ flanking regions of these aEPEC isolates were identical to the respective region in the STEC O156:H25 isolates, the core genome, the virulence associated genome regions and the CRISPR/CAS elements differed profoundly. Our cumulative epidemiological and molecular data suggests a recent switch of the O-AGC between isolates with O156:H8 strains having served as DNA donors. Such O-antigen switches can affect the evaluation of a strain's pathogenic and virulence potential, suggesting that NGS methods might lead to a more reliable risk assessment
Conductivity in a symmetry broken phase: Spinless fermions with corrections
The dynamic conductivity of strongly correlated electrons in
a symmetry broken phase is investigated in the present work. The model
considered consists of spinless fermions with repulsive interaction on a simple
cubic lattice. The investigated symmetry broken phase is the charge density
wave (CDW) with wave vector which occurs at
half-filling. The calculations are based on the high dimensional approach, i.e.
an expansion in the inverse dimension is used. The finite dimensionality
is accounted for by the inclusion of linear terms in and the true finite
dimensional DOS. Special care is paid to the setup of a conserving
approximation in the sense of Baym/Kadanoff without inconsistencies. The
resulting Bethe-Salpeter equation is solved for the dynamic conductivity in the
non symmetry broken and in the symmetry broken phase (AB-CDW). The
dc-conductivity is reduced drastically in the CDW. Yet it does not vanish in
the limit due to a subtle cancellation of diverging mobility and
vanishing DOS. In the dynamic conductivity the energy gap
induced by the symmetry breaking is clearly discernible. In addition, the
vertex corrections of order lead to an excitonic resonance lying within
the gap.Comment: 23 pages, 19 figures included with psfig, Revtex; Physical Review
B15, in press (October/November 1996) depending on the printer/screen driver,
it might be necessary to comment out figures 3,4,5,10,11,12,19 and have them
printed separatel
Dynamical correlations in multiorbital Hubbard models: Fluctuation-exchange approximations
We study the two band degenerate Hubbard model using the Fluctuation Exchange
approximation (FLEX) method and compare the results with Quantum Monte-Carlo
calculations. Both the self-consistent and the non-self-consistent versions of
the FLEX scheme are investigated. We find that, contrary to the one band case,
in the multiband case, good agreement with the Quantum Monte-Carlo results is
obtained within the electron-electron T-matrix approximation using the full
renormalization of the one-particle propagators. The crossover to strong
coupling and the formation of satellites is more clearly visible in the
non-self-consistent scheme. Finally we discuss the behavior of the FLEX for
higher orbital degeneracy.Comment: 18 pages with 12 PS figure
Characterization of the binding site of the histamine H3 receptor. 1. Various approaches to the synthesis of 2-(1H-imidazol-4-yl)cyclopropylamine and histaminergic activity of (1R,2R)-and (1S,2S)-2-(1H-imidazol-4-yl)-cyclopropylamine.
Various approaches to the synthesis of all four stereoisomers of 2-(1H- imidazol-4-yl)cyclopropylamine (cyclopropylhistamine) are described. The rapid and convenient synthesis and resolution of trans-cyclopropylhistamine is reported. The absolute configuration of its enantiomers was determined by single-crystal X-ray crystallographic analysis. The distinct transcyclopropylhistamine enantiomers were tested for their activity and affinity on the histamine
Unified description of Fermi and non-Fermi liquid behavior in a conserving slave boson approximation for strongly correlated impurity models
We show that the presence of Fermi or non-Fermi liquid behavior in the SU(N)
x SU(M) Anderson impurity models may be read off the infrared threshold
exponents governing the spinon and holon dynamics in a slave boson
representation of these models. We construct a conserving T-matrix
approximation which recovers the exact exponents with good numerical accuracy.
Our approximation includes both coherent spin flip scattering and charge
fluctuation processes. For the single-channel case the tendency to form bound
states drastically modifies the low energy behavior. For the multi-channel case
in the Kondo limit the bound state contributions are unimportant.Comment: 4 pages, Latex, 3 postscript figures included Final version with
minor changes in wording, to appear in Phys.Rev.Let
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