730 research outputs found

    DY determinants, possibly associated with novel class II molecules, stimulate autoreactive CD4+ T cells with suppressive activity

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    A set of T cell clones (TCC) isolated from HLA-DR-, Dw-, DQ-matched allogeneic MLCs was found to proliferate autonomously when stimulated with cells carrying a wide range of class I or II specificities. This apparently unrestricted proliferation was relatively weak, and only low levels of IL-2 were present in the supernatants of stimulated cells. Autologous as well as allogeneic PBMC and B lymphoblastoid cell lines (B-LCL) were capable of stimulating such clones, which were also restimulated by suppressive, but not by helper, TCC. Moreover, such clones displayed the unusual property of autostimulation. mAb inhibition experiments suggested that class II- or class II-restricted antigens were involved in stimulation. Thus, certain "broad" mAbs (TU39, SG520) reacting with multiple locus products inhibited activation of these reagents, but none of those reacting more specifically with DR (TU34, TU37, L243, Q2/70, SG157), DQ (TU22, SPV- L3, Leu 10), or DP (B7/21), or mixtures of these mAbs, were able to do so. Evidence from sequential immunoprecipitation experiments suggested that mAb TU39 bound class II-like molecules other than DR, DQ, and DP on TCC and B-LCL, and it is therefore proposed that such putative novel class II-like molecules may carry the stimulating determinants for these autoreactive clones. DY-reactive clones lacked helper activity for B cells but mediated potent suppressive activity on T cell proliferative responses that was not restricted by the HLA type of the responding cells. Suppressive activity was induced in normal PBMC by such clones, as well as by independent suppressive clones, which was also inhibited only by mAb TU39. These findings lead to the proposal that DY-reactive autostimulatory cells may constitute a self- maintaining suppressive circuit, the level of activity of which would be regulated primarily by the availability of IL-2 in the microenvironmen

    "Tolerization" of human T-helper cell clones by chronic exposure to alloantigen

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    Induction of clonal anergy in T-helper (Th) cells may have a role in regulating immune responses. A model system for studying Th cell tolerization at the clonal level in vitro could be useful for investigating the mechanisms involved. Accordingly, alloreactive helper cells were maintained in culture with interleukin 2 (IL 2) by intermittent stimulation with specific antigen. Regardless of the frequency of antigen stimulation, clones of age less than ca. 35 population doublings (PD) were found to undergo antigen-specific autocrine clonal expansion in the absence of exogenous IL 2. Such young clones (designated as phase I) could therefore not be "tolerized" by frequent exposure to antigen. In contrast, most clones of age greater than ca. 35 PD could be tolerized by frequent exposure to antigen (designated as phase II clones). Their autocrine proliferation was then blocked, although they still recognized antigen specifically as shown by their retained ability to secrete interferon-gamma (IFN-gamma) and granulocyte-macrophage colony stimulating factor (GM-CSF). The mechanism of response failure involved both an inability to upregulate IL 2 receptors in the absence of exogenous IL 2, as well as an inability to secrete IL 2. These defects were not overcome by stimulation with mitogens or calcium ionophore and phorbol esther in place of alloantigen. T-cell receptor, alpha, beta, and gamma-chain gene rearrangements remained identical in phase I and phase II clones. Tolerization of phase II clones could be avoided by increasing the period between antigen exposures. Despite this, whether or not phase II cells were capable of autocrine proliferation, they were found to have acquired the novel function of inducing suppressive activity in fresh lymphocytes. Suppressor-induction was blocked by the broadly reactive MHC class II-specific monoclonal antibody (moAb) TU39, but not by moAb preferentially reacting only with HLA-DR, DQ, or DP. Sequential immunoprecipitation on T-cell clones showed the presence of a putative non-DR, DQ, DP, TU39+ molecule on phase II clones. However, this molecule was also found on phase I clones. The nature of the TU39-blockable suppressor-inducing determinant present on phase II but not on (most) phase I clones thus remains to be clarified. In addition to suppressor-induction activity, phase II clones also acquired lytic potential as measured in a lectin approximation system. Cytotoxic (CTX) potential was also not influenced by the frequency of antigenic stimulation and could be viewed as a constitutive modulation of clonal functio

    Software for Acquiring Image Data for PIV

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    PIV Acquisition (PIVACQ) is a computer program for acquisition of data for particle-image velocimetry (PIV). In the PIV system for which PIVACQ was developed, small particles entrained in a flow are illuminated with a sheet of light from a pulsed laser. The illuminated region is monitored by a charge-coupled-device camera that operates in conjunction with a data-acquisition system that includes a frame grabber and a counter-timer board, both installed in a single computer. The camera operates in "frame-straddle" mode where a pair of images can be obtained closely spaced in time (on the order of microseconds). The frame grabber acquires image data from the camera and stores the data in the computer memory. The counter/timer board triggers the camera and synchronizes the pulsing of the laser with acquisition of data from the camera. PIVPROC coordinates all of these functions and provides a graphical user interface, through which the user can control the PIV data-acquisition system. PIVACQ enables the user to acquire a sequence of single-exposure images, display the images, process the images, and then save the images to the computer hard drive. PIVACQ works in conjunction with the PIVPROC program which processes the images of particles into the velocity field in the illuminated plane

    Determining Sizes of Particles in a Flow from DPIV Data

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    A proposed method of measuring the size of particles entrained in a flow of a liquid or gas would involve utilization of data from digital particle-image velocimetry (DPIV) of the flow. That is to say, with proper design and operation of a DPIV system, the DPIV data could be processed according to the proposed method to obtain particle sizes in addition to particle velocities. As an additional benefit, one could then compute the mass flux of the entrained particles from the particle sizes and velocities. As in DPIV as practiced heretofore, a pulsed laser beam would be formed into a thin sheet to illuminate a plane of interest in a flow field and the illuminated plane would be observed by means of a charge-coupled device (CCD) camera aimed along a line perpendicular to the illuminated plane. Unlike in DPIV as practiced heretofore, care would be taken to polarize the laser beam so that its electric field would lie in the illuminated plane, for the reason explained in the next paragraph. The proposed method applies, more specifically, to transparent or semitransparent spherical particles that have an index of refraction different from that of the fluid in which they are entrained. The method is based on the established Mie theory, which describes the scattering of light by diffraction, refraction, and specular reflection of light by such particles. In the case of a particle illuminated by polarized light and observed in the arrangement described in the preceding paragraph, the Mie theory shows that the image of the particle on the focal plane of the CCD camera includes two glare spots: one attributable to light reflected toward the camera and one attributable to light refracted toward the camera. The distance between the glare spots is a known function of the size of the particle, the indices of refraction of the particle material, and design parameters of the camera optics. Hence, the size of a particle can be determined from the distance between the glare spots. The proposed method would be implemented in an algorithm that would automatically identify, and measure the distance between, the glare spots for each particle for which a suitable image has been captured in a DPIV image frame. The algorithm (see figure) would begin with thresholding of data from the entire image frame to reduce noise, thereby facilitating discrimination of particle images from the background and aiding in the separation of overlapping particles. It is important not to pick a threshold level so high that the light intensity between a given pair of glare spots does not fall below the threshold value, leaving the glare spots disconnected. The image would then be scanned in a sequence of rows and columns of pixels to identify groups of adjacent pixels that contain nonzero brightnesses and that are surrounded by pixels of zero brightness. Each such group would be assumed to constitute the image of one particle. Each such group would be further analyzed to determine whether the image was saturated; saturated particle images must be rejected because the locations of glare spots in saturated images cannot accurately be determined. Within each unsaturated particle image, the centroids (deemed to be the locations) of the glare spots would be determined by means of gradients of brightness distributions and three-point horizontal and three-point vertical Gaussian estimates based on the brightness values of the brightest pixels and the pixels adjacent to them. If the brightness of a given particle image contained only one peak, then it would be assumed that a second glare spot did not exist and that image would be rejected

    Laser Anemometer Measurements of the Flow Field in a 4:1 Pressure Ratio Centrifugal Impeller

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    A laser-doppler anemometer was used to obtain flow-field velocity measurements in a 4:1 pressure ratio, 4.54 kg/s (10 lbm/s), centrifugal impeller, with splitter blades and backsweep, which was configured with a vaneless diffuser. Measured through-flow velocities are reported for ten quasi-orthogonal survey planes at locations ranging from 1% to 99% of main blade chord. Measured through-flow velocities are compared to those predicted by a 3-D viscous steady flow analysis (Dawes) code. The measurements show the development and progression through the impeller and vaneless diffuser of a through-flow velocity deficit which results from the tip clearance flow and accumulation of low momentum fluid centrifuged from the blade and hub surfaces. Flow traces from the CFD analysis show the origin of this deficit which begins to grow in the inlet region of the impeller where it is first detected near the suction surface side of the passage. It then moves toward the pressure side of the channel, due to the movement of tip clearance flow across the impeller passage, where it is cut by the splitter blade leading edge. As blade loading increases toward the rear of the channel the deficit region is driven back toward the suction surface by the cross-passage pressure gradient. There is no evidence of a large wake region that might result from flow separation and the impeller efficiency is relatively high. The flow field in this impeller is quite similar to that documented previously by NASA Lewis in a large low-speed backswept impeller

    Inclusion scolaire : dispositif pédagogique pour enfants dyslexiques et dysphasiques au sein d'une école spécialisée

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    International audienceIn the first part of the article, we describe different types of schooling in France, for children withdisabilities. In the second part, we focus on a particular system of teaching - a local unit for inclusiveeducation - for children aged from 6 to 12 with specific language disorders and learning disabilities,in a specialised school. In the last part, we describe a few exemples of pedagogical accomodationsconceived for the local unit for inclusive education and other accomodations designed to be used inthe inclusion class in history and geography studies.Dans la première partie de l’article, nous décrivons les différents types de scolarisation, en France,pour des élèves en situation de handicap. Dans une deuxième partie, nous présentons un dispositifpédagogique - une Unité locale pour l’inclusion scolaire - mis en place pour l’accompagnementd’élèves âgés de 6 à 12 ans présentant des troubles spécifiques du langage et des apprentissages, cela,au sein d’une école spécialisée. Dans une dernière partie, nous décrivons quelques exemplesd’adaptations pédagogiques menées au sein de ce dispositif ainsi que d’autres adaptations menéesdans la classe de référence des élèves en histoire-géographie

    X-ray Raman scattering study of aligned polyfluorene

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    We present a non-resonant inelastic x-ray scattering study at the carbon K-edge on aligned poly[9,9-bis(2-ethylhexyl)-fluorene-2,7-diyl] and show that the x-ray Raman scattering technique can be used as a practical alternative to x-ray absorption measurements. We demonstrate that this novel method can be applied to studies on aligned π\pi-conjugated polymers complementing diffraction and optical studies. Combining the experimental data and a very recently proposed theoretical scheme we demonstrate a unique property of x-ray Raman scattering by performing the symmetry decomposition on the density of unoccupied electronic states into ss- and pp-type symmetry contributions.Comment: 19 pages, 8 figure
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