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Background Suppression (background + suppression)
Selected AbstractsSeasonal changes in suppressive capacity of CD4+ CD25+ T cells from patients with hayfever are allergen-specific and may result in part from expansion of effector T cells among the CD25+ populationCLINICAL & EXPERIMENTAL ALLERGY, Issue 11 2009A. E. Anderson Summary Background Suppression of allergen-stimulated peripheral blood CD4+ CD25, effector T cells by CD4+ CD25+ regulatory T cells obtained from subjects with allergic rhinoconjunctivitis is reduced during the pollen season when compared with out of season. Objective We examined possible explanations for this effect of seasonal pollen exposure on suppression of allergen responses. Methods CD4+ CD25, and CD4+ CD25+ T cells were isolated from blood obtained from 44 volunteers with allergic rhinoconjunctivitis during and out of the UK grass pollen season. Co-cultures were performed with grass pollen extract and house dust mite (HDM) to examine allergen specificity. The frequency of IL-5 and IL-10 producing cells was determined by ELISPOT and the expression of T cell activation markers and the CD25+ regulatory T cell-associated transcription factor Foxp3 were examined. Lactic acid stripping of IgE was used to determine IgE dependence of T cell responses. Results The seasonal reduction in suppression by CD4+ CD25+ T cells was confirmed and was shown to be allergen specific because suppression of HDM-stimulated cultures was not affected significantly. The CD4+ CD25+ population contained IL-5 and IL-10 producing cells but increases in their frequencies with seasonal pollen exposure were not significant. Both activation marker and Foxp3 expression increased during the pollen season. IgE stripping reduced CD4+ and CD4+ CD25, T cell responses to allergen, but had no effect on suppression by CD4+ CD25+ T cells. Conclusion The seasonal reduction in suppression of grass pollen-stimulated effector T cells by CD4+ CD25+ T cells is allergen specific and cannot be explained by increased IgE-facilitated allergen presentation. We suggest that changes in the proportion of effector to regulatory T cells among the CD25+ population isolated may partially explain these findings, and that trafficking to the site of allergic disease may reduce allergen-specific regulatory T cell numbers in peripheral blood. [source] Two-beam multiplexed CARS based on a broadband oscillator,JOURNAL OF RAMAN SPECTROSCOPY, Issue 8 2010Kentaro Furusawa Abstract A two-beam multiplexed coherent anti-Stokes Raman scattering (CARS) microscopy setup is demonstrated by using a broadband (BB) Ti:sapphire oscillator without using any specialty fibres. A well-defined spectral structure of the source leads to a delay-sensitive CARS measurement in two-colour CARS and also provides an efficient means of obtaining three-colour CARS signals combined with the dispersion compensation of the BB pulse. Our result implies that the background suppression is limited by the onset of the spurious signals caused by the different CARS process, qualitatively differing from what is typically observed in the CARS microscopy. Copyright © 2010 John Wiley & Sons, Ltd. [source] Fluorescence background suppression in Raman spectroscopy using combined Kerr gated and shifted excitation Raman difference techniquesJOURNAL OF RAMAN SPECTROSCOPY, Issue 4 2002P. Matousek An exceptionally high level of fluorescence rejection from resonance Raman spectra was achieved using a combination of two techniques, namely Kerr gated temporal rejection with shifted excitation Raman difference spectroscopy. The method was able to recover the resonance Raman spectrum from the intense fluorescence background with a signal-to-noise ratio at least 10 times higher than that achievable with either of the two approaches used individually. To demonstrate the effectiveness of the technique we obtained the resonance Raman spectrum of the laser dye rhodamine 6G (1 × 10,3 mol dm,3) in methanol by excitation at 532 nm and measuring under the maximum of fluorescence emission at 560,590 nm. The method reached the photon shot noise limit of the residual fluorescence providing a detection limit for Raman spectra 106 times lower than the original fluorescence intensity in an accumulation time of 800 s. A unique feature of the experiment was the way in which the optical parametric amplifier light source was configured to alternate automatically between the two excitation wavelengths using an optogalvanic mirror arrangement. The ultra-high sensitivity of the combined approach holds great promise for selective probing of complex biological systems using resonance Raman spectroscopy. Copyright © 2002 John Wiley & Sons, Ltd. [source] View ordering for magnetization prepared steady state free precession acquisition: Application in contrast-enhanced MR angiographyMAGNETIC RESONANCE IN MEDICINE, Issue 3 2004Pascal Spincemaille Abstract Magnetization prepared segmented acquisition requires a view order that maximizes signal contrast during the acquisition of the central portion of k -space. Steady state free precession (SSFP) acquisition further requires a view order that minimizes changes in phase-encoding gradients from one repetition to the next in order to minimize eddy current artifacts. In this article, optimal view ordering schemes satisfying these two requirements are formulated and applied to inversion prepared 3D SSFP contrast-enhanced MR angiography (MRA). Experiments on phantoms and pigs demonstrated improved background suppression and reduced image artifacts. Magn Reson Med 52:461,466, 2004. © 2004 Wiley-Liss, Inc. [source] | ||||||||||