IgM

Distribution by Scientific Domains
Distribution within Medical Sciences

Kinds of IgM

  • anti-hev igm
  • serum igm

  • Terms modified by IgM

  • igm antibody
  • igm level
  • igm response

  • Selected Abstracts


    Brachial-ankle pulse wave velocity and cardiovascular risk factors in the non-diabetic and newly diagnosed diabetic Chinese: Guangzhou Biobank Cohort Study-CVD

    DIABETES/METABOLISM: RESEARCH AND REVIEWS, Issue 2 2010
    Lin Xu
    Abstract Background Increased arterial stiffness is an important cause of cardiovascular disease (CVD). We examined determinants of arterial stiffness in subjects across strata of glycaemic status. Methods A total of 1249 subjects from a sub-study of the Guangzhou Biobank Cohort Study (GBCS-CVD) had brachial-ankle pulse wave velocity (baPWV) measured by automatic oscillometric method. Major cardiovascular risk factors including glycosylated haemoglobin A1c (HbA1c), high sensitivity C-reactive protein (hsCRP), fasting triglyceride, low- and high-density lipoprotein cholesterol and both fasting and post 2-h oral glucose-load glucose, systolic and diastolic blood pressure were assessed. Results In all, 649, 479 and 121 subjects were classified into normoglycaemia, impaired glucose metabolism (IGM) and newly diagnosed diabetes groups, respectively. Both age and systolic blood pressure were significantly associated with increased baPWV in all three groups (all p < 0.001). In both normoglycaemic and IGM groups, hsCRP and HbA1c were positively associated with baPWV (p from 0.04 to < 0.001), whereas current smoking and triglyceride were associated with baPWV in the normoglycaemic and IGM group, respectively (p = 0.04 and 0.001). No gender difference in baPWV was observed in the normoglycaemic or IGM groups. However, in the newly diagnosed diabetes group, men had higher baPWV than women (p = 0.01). Conclusions In the normoglycaemic and IGM subjects, after adjusting for age, blood pressure and other confounders, increasing HbA1c was associated with increased baPWV, suggesting a pathophysiological role of chronic glycaemia that can contribute to vascular disease risk in persons without diabetes. Copyright © 2010 John Wiley & Sons, Ltd. [source]


    Idiopathic polyneuropathy and impaired glucose metabolism in a Norwegian patient series

    EUROPEAN JOURNAL OF NEUROLOGY, Issue 8 2008
    M. Nebuchennykh
    Background and purpose:, North American studies have indicated a high prevalence of impaired glucose tolerance (IGT) in patients with sensory polyneuropathy. We searched for the occurrence of IGT in a Norwegian patient material with polyneuropathy. Methods:, Seventy patients with symptoms and signs of sensory polyneuropathy were included. Cases with known causes of neuropathy were excluded. All patients underwent a 2 h oral glucose tolerance test (OGTT). Nerve conduction studies (NCS), quantitative sensory testing (QST) and skin biopsy with assessment of intra-epidermal nerve fibre (IENF) density were performed. Results:, Sixteen patients (23%) had impaired glucose metabolism (IGM): 2 (3%) were found to have diabetes, 9 (13%) had IGT, 3 (4%) had impaired fasting glucose (IFG) and 2 (3%) both IFG and IGT. About 62% of the patients with IGM and polyneuropathy and 50% of those with chronic idiopathic axonal polyneuropathy (CIAP) had abnormalities on NCS. Reduction of IENF occurred in 37% of the patients with IGM and 43% of those with CIAP. Conclusions:, Patients with polyneuropathy and IGM had essentially the same degree of involvement of small and large nerve fibres as patients with CIAP. IGT seems less frequent in Norwegian patients with polyneuropathy than reported in North American populations. [source]


    Modification of the 21-cm power spectrum by X-rays during the epoch of reionization

    MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 2 2009
    L. Warszawski
    ABSTRACT We incorporate a contribution to reionization from X-rays within analytic and seminumerical simulations of the 21-cm signal arising from neutral hydrogen during the epoch of reionization. The relatively long X-ray mean free path (MFP) means that ionizations due to X-rays are not subject to the same density bias as UV ionizations, resulting in a substantive modification to the statistics of the 21-cm signal. We explore the impact that X-ray ionizations have on the power spectrum (PS) of 21-cm fluctuations by varying both the average X-ray MFP and the fractional contribution of X-rays to reionization. In general, prior to the epoch when the intergalactic medium (IGM) is dominated by ionized regions (H ii regions), X-ray-induced ionization enhances fluctuations on spatial scales smaller than the X-ray MFP, provided that X-ray heating does not strongly suppress galaxy formation. Conversely, at later times when H ii regions dominate, small-scale fluctuations in the 21-cm signal are suppressed by X-ray ionization. Our modelling also shows that the modification of the 21-cm signal due to the presence of X-rays is sensitive to the relative scales of the X-ray MFP and the characteristic size of H ii regions. We therefore find that X-rays imprint an epoch and scale-dependent signature on the 21-cm PS, whose prominence depends on fractional X-ray contribution. The degree of X-ray heating of the IGM also determines the extent to which these features can be discerned. We further show that the presence of X-rays smoothes out the shoulder-like signature of H ii regions in the 21-cm PS. For example, a 10 per cent contribution to reionization from X-rays translates to a 20,30 per cent modulation in the 21-cm PS across the scale of H ii regions. We show that the Murchison Widefield Array will have sufficient sensitivity to detect this modification of the PS, so long as the X-ray photon MFP falls within the range of scales over which the array is most sensitive (,0.1 Mpc,1). In cases in which this MFP takes a much smaller value, an array with larger collecting area would be required. As a result, an X-ray contribution to reionization has the potential to substantially complicate analysis of the 21-cm PS. On the other hand, a combination of precision measurements and modelling of the 21-cm PS promises to provide an avenue for investigating the role and contribution of X-rays during reionization. [source]


    Is AGN feedback necessary to form red elliptical galaxies?

    MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 1 2008
    A. Khalatyan
    ABSTRACT We have used the smoothed particle hydrodynamics (SPH) code gadget-2 to simulate the formation of an elliptical galaxy in a group-size cosmological dark matter halo with mass Mhalo, 3 × 1012 h,1 M, at z= 0. The use of a stellar population synthesis model has allowed us to compute magnitudes, colours and surface brightness profiles. We have included a model to follow the growth of a central black hole and we have compared the results of simulations with and without feedback from active galactic nuclei (AGN). We have studied the interplay between cold gas accretion and merging in the development of galactic morphologies, the link between colour and morphology evolution, the effect of AGN feedback on the photometry of early-type galaxies, the redshift evolution in the properties of quasar hosts, and the impact of AGN winds on the chemical enrichment of the intergalactic medium (IGM). We have found that the early phases of galaxy formation are driven by the accretion of cold filamentary flows, which form a disc galaxy at the centre of the dark matter halo. Disc star formation rates in this mode of galaxy growth are about as high as the peak star formation rates attained at a later epoch in galaxy mergers. When the dark matter halo is sufficiently massive to support the propagation of a stable shock, the gas in the filaments is heated to the virial temperature, cold accretion is shut down, and the star formation rate begins to decline. Mergers transform the spiral galaxy into an elliptical one, but they also reactivate star formation by bringing gas into the galaxy. Without a mechanism that removes gas from the merger remnants, the galaxy ends up with blue colours, which are atypical for its elliptical morphology. We have demonstrated that AGN feedback can solve this problem even with a fairly low heating efficiency. Our simulations support a picture where AGN feedback is important for quenching star formation in the remnant of wet mergers and for moving them to the red sequence. This picture is consistent with recent observational results, which suggest that AGN hosts are galaxies in migration from the blue cloud to the red sequence on the colour,magnitude diagram. However, we have also seen a transition in the properties of AGN hosts from blue and star forming at z, 2 to mainly red and dead at z, 0. Ongoing merging is the primary but not the only triggering mechanism for luminous AGN activity. Quenching by AGN is only effective after the cold filaments have dried out, since otherwise the galaxy is constantly replenished with gas. AGN feedback also contributes to raising the entropy of the hot IGM by removing low-entropy tails vulnerable to developing cooling flows. We have also demonstrated that AGN winds are potentially important for the metal enrichment of the IGM a high redshift. [source]


    Redshifted 21-cm observations of high-redshift quasar proximity zones

    MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 1 2008
    J. Stuart B. Wyithe
    ABSTRACT The introduction of low-frequency radio arrays is expected to revolutionize the study of the reionization epoch. Observation of the contrast in redshifted 21-cm emission between a large H ii region and the surrounding neutral intergalactic medium (IGM) will be the simplest and most easily interpreted signature. However, the highest redshift quasars known are thought to reside in an ionized IGM. Using a semi-analytic model we describe the redshifted 21-cm signal from the IGM surrounding quasars discovered using the i -drop-out technique (i.e. quasars at z, 6). We argue that while quasars at z < 6.5 seem to reside in the post-overlap IGM, they will still provide valuable probes of the late stages of the overlap era because the light-travel time across a quasar proximity zone should be comparable to the duration of overlap. For redshifted 21-cm observations within a 32-MHz bandpass, we find that the subtraction of a spectrally smooth foreground will not remove spectral features due to the proximity zone. These features could be used to measure the neutral hydrogen content of the IGM during the late stages of reionization. The density of quasars at z, 6 is now well constrained. We use the measured quasar luminosity function to estimate the prospects for discovery of high-redshift quasars in fields that will be observed by the Murchison Widefield Array. [source]


    Ly, leaks and reionization

    MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 4 2008
    Longlong Feng
    ABSTRACT Ly, absorption spectra of QSOs at redshifts z, 6 show complete Gunn,Peterson absorption troughs (dark gaps) separated by tiny leaks. The dark gaps are from the intergalactic medium (IGM) where the density of neutral hydrogen are high enough to produce almost saturated absorptions, however, where the transmitted leaks come from is still unclear so far. We demonstrate that leaking can originate from the lowest density voids in the IGM as well as the ionized apatches around ionizing sources using semi-analytical simulations. If leaks are produced in lowest density voids, the IGM must already be highly ionized, and the ionizing background should be almost uniform; in contrast, if leaks come from ionized patches, the neutral fraction of IGM should be still high, and the ionizing background is significantly inhomogeneous. Therefore, the origin of leaking is crucial to determining the epoch of inhomogeneous-to-uniform transition of the ionizing photon background. We show that the origin could be studied with the statistical features of leaks. Actually, Ly, leaks can be well defined and described by the equivalent width W and the full width of half-area WH, both of which are less contaminated by instrumental resolution and noise. It is found that the distributions of W and WH of Ly, leaks are sensitive to the modelling of the ionizing background. We consider four representative models: uniform ionizing background (model 0), the photoionization rate of neutral hydrogen ,H i and the density of IGM are either linearly correlated (model I), or anticorrelated (model II), and ,H i is correlated with high-density peaks containing ionizing sources (model III). Although all of these models can match to the mean of the observed effective optical depth of the IGM at z, 6, the distributions of W and WH are very different from each other. Consequently, the leak statistics provides an effective tool to probe the evolutionary history of reionization at z, 5,6.5. Similar statistics will also be applicable to the reionization of He ii at z, 3 [source]


    Reionization bias in high-redshift quasar near-zones

    MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 2 2008
    J. Stuart B. Wyithe
    ABSTRACT Absorption spectra of high-redshift quasars exhibit an increasingly thick Ly, forest, suggesting that the fraction of neutral hydrogen in the intergalactic medium (IGM) is increasing towards z, 6. However, the interpretation of these spectra is complicated by the fact that the Ly, optical depth is already large for neutral hydrogen fractions in excess of 10,4, and also because quasars are expected to reside in dense regions of the IGM. We present a model for the evolution of the ionization state of the IGM which is applicable to the dense, biased regions around high-redshift quasars as well as more typical regions in the IGM. We employ a cold dark matter based model in which the ionizing photons for reionization are produced by star formation in dark matter haloes spanning a wide range of masses, combined with numerical radiative transfer simulations which model the resulting opacity distribution in quasar absorption spectra. With an appropriate choice for the parameter which controls the star formation efficiency, our model is able to simultaneously reproduce the observed Ly, forest opacity at 4 < z < 6, the ionizing photon mean-free-path at z, 4 and the rapid evolution of highly ionized near-zone sizes around high-redshift quasars at 5.8 < z < 6.4. In our model, reionization extends over a wide redshift range, starting at z, 10 and completing as H ii regions overlap at z, 6,7. We find that within 5 physical Mpc of a high-redshift quasar, the evolution of the ionization state of the IGM precedes that in more typical regions by around 0.3 redshift units. More importantly, when combined with the rapid increase in the ionizing photon mean-free-path expected shortly after overlap, this offset results in an ionizing background near the quasar which exceeds the value in the rest of the IGM by a factor of ,2,3. We further find that in the post-overlap phase of reionization the size of the observed quasar near-zones is not directly sensitive to the neutral hydrogen fraction of the IGM. Instead, these sizes probe the level of the background ionization rate and the temperature of the surrounding IGM. The observed rapid evolution of the quasar near-zone sizes at 5.8 < z < 6.4 can thus be explained by the rapid evolution of the ionizing background, which in our model is caused by the completion of overlap at the end of reionization by 6 ,z, 7. [source]


    H i imaging of galaxies in X-ray bright groups

    MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 1 2007
    Chandreyee Sengupta
    ABSTRACT Environment plays an important role in the evolution of the gas contents of galaxies. Gas deficiency of cluster spirals and the role of the hot intracluster medium in stripping gas from these galaxies is a well-studied subject. Loose groups with diffuse X-ray emission from the intragroup medium (IGM) offer an intermediate environment between clusters and groups without a hot IGM. These X-ray bright groups have smaller velocity dispersion and lower temperature than clusters, but higher IGM density than loose groups without diffuse X-ray emission. A single-dish comparative study of loose groups with and without diffuse X-ray emission from the IGM, showed that the galaxies in X-ray bright groups have lost more gas on average than the galaxies in non X-ray bright groups. In this paper we present GMRT H i observations of 13 galaxies from four X-ray bright groups: NGC 5044, 720, 1550 and IC1459. The aim of this work is to study the morphology of H i in these galaxies and to see if the hot IGM has in any way affected their H i content or distribution. In addition to disturbed H i morphology, we find that most galaxies have shrunken H i discs compared to the field spirals. This indicates that IGM-assisted stripping processes like ram pressure may have stripped gas from the outer edges of the galaxies. [source]


    Hot and cold gas accretion and feedback in radio-loud active galaxies

    MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 4 2007
    M. J. Hardcastle
    ABSTRACT We have recently shown that X-ray observations of the population of ,low-excitation' radio galaxies, which includes most low-power, Fanaroff,Riley class I sources as well as some more powerful Fanaroff,Riley class II objects, are consistent with a model in which the active nuclei of these objects are not radiatively efficient at any waveband. In another recent paper, Allen et al. have shown that Bondi accretion of the hot, X-ray emitting phase of the intergalactic medium (IGM) is sufficient to power the jets of several nearby, low-power radio galaxies at the centres of clusters. In this paper, we combine these ideas and suggest that accretion of the hot phase of the IGM is sufficient to power all low-excitation radio sources, while high-excitation sources are powered by accretion of cold gas that is in general unrelated to the hot IGM. This model explains a number of properties of the radio-loud active galaxy population, and has important implications for the energy input of radio-loud active galactic nuclei into the hot phase of the IGM: the energy supply of powerful high-excitation sources does not have a direct connection to the hot phase. [source]


    Cosmological simulations of intergalactic medium enrichment from galactic outflows

    MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 4 2006
    Benjamin D. Oppenheimer
    ABSTRACT We investigate models of self-consistent chemical enrichment of the intergalactic medium (IGM) from z= 6.0 , 1.5, based on hydrodynamic simulations of structure formation that explicitly incorporate outflows from star-forming galaxies. Our main result is that outflow parametrizations derived from observations of local starburst galaxies, in particular momentum-driven wind scenarios, provide the best agreement with observations of C iv absorption at z, 2,5. Such models sufficiently enrich the high- z IGM to produce a global mass density of C iv absorbers that is relatively invariant from z= 5.5 , 1.5, in agreement with observations. This occurs despite continual IGM enrichment causing an increase in volume-averaged metallicity by ,× 5,10 over this redshift range, because energy input accompanying the enriching outflows causes a drop in the global ionization fraction of C iv. Comparisons to observed C iv column density and linewidth distributions and C iv -based pixel optical depth ratios provide significant constraints on wind models. Our best-fitting outflow models show mean IGM temperatures only slightly above our no-outflow case, metal filling factors of just a few per cent with volume-weighted metallicities around 10,3 at z, 3, significant amounts of collisionally ionized C iv absorption and a metallicity,density relationship that rises rapidly at low overdensities and flattens at higher ones. In general, we find that outflow speeds must be high enough to enrich the low-density IGM at early times but low enough not to overheat it, and concurrently must significantly suppress early star formation while still producing enough early metals. It is therefore non-trivial that locally calibrated momentum-driven wind scenarios naturally yield the desired strength and evolution of outflows, and suggest that such models represent a significant step towards understanding the impact of galactic outflows on galaxies and the IGM across cosmic time. [source]


    Cosmic evolution of metal densities: the enrichment of the intergalactic medium

    MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 1 2006
    F. Calura
    ABSTRACT By means of chemo-photometric models for galaxies of different morphological types, we have carried out a detailed study of the history of element production by spheroidal and dwarf irregular galaxies. Spheroidal galaxies suffer a strong and intense star formation episode at early times. In dwarf irregulars, the star formation rate (SFR) proceeds at a low regime but continuously. Both galactic types enrich the intergalactic medium (IGM) with metals by means of galactic winds. We have assumed that the galaxy number density is fixed and normalized to the value of the optical luminosity function observed in the local Universe. Our models allow us to investigate in detail how the metal fractions locked up in stars in spheroids and dwarf irregulars, those present in the interstellar medium (ISM) and those ejected into the IGM have changed with cosmic time. By relaxing the instantaneous recycling approximation and taking into account stellar lifetimes, for the first time we have studied the evolution of the chemical abundance ratios in the IGM and compared our predictions with a set of observations by various authors. Our results indicate that the bulk of the IGM enrichment is due to spheroids, with dwarf irregular galaxies playing a negligible role. Our predictions grossly account for the [O/H] observed in the IGM at high redshift, but overestimate the [C/H]. Furthermore, it appears hard to reproduce the abundance ratios observed in the high-redshift IGM. Some possible explanations are discussed in the text. This is the first attempt to study the abundance ratios in the IGM by means of detailed chemical evolution models which take into account the stellar lifetimes. Numerical simulations adopting our chemical evolution prescriptions could be useful to improve our understanding of the IGM chemical enrichment. [source]


    The sources of intergalactic metals

    MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 2 2006
    E. Scannapieco
    ABSTRACT We study the clustering properties of metals in the intergalactic medium (IGM) as traced by 619 C iv and 81 Si iv absorption components with N, 1012 cm,2 and 316 Mg ii and 82 Fe ii absorption components with N, 1011.5 cm,2 in 19 high signal-to-noise ratio (60,100 pixel,1), high-resolution (R= 45 000) quasar spectra. C iv and Si iv trace each other closely and their line-of-sight correlation functions ,(v) exhibit a steep decline at large separations and a flatter profile below ,150 km s,1, with a large overall bias. These features do not depend on absorber column densities, although there are hints that the overall amplitude of ,C iv (v) increases with time over the redshift range detected (1.5,3). Carrying out a detailed smoothed particle hydrodynamic simulation (2 × 3203, 57 Mpc3 comoving), we show that the C iv correlation function cannot be reproduced by models in which the IGM metallicity is constant or a local function of overdensity (Z,,2/3). However, the properties of ,C iv(v) are generally consistent with a model in which metals are confined within bubbles with a typical radius Rs about sources of mass ,Ms. We derive best-fitting values of Rs, 2 comoving Mpc and Ms, 1012 M, at z= 3. Our lower-redshift (0.5,2) measurements of the Mg ii and Fe ii correlation functions also uncover a steep decline at large separations and a flatter profile at small separations, but the clustering is even higher than in the z= 1.5,3 measurements, and the turnover is shifted to somewhat smaller distances, ,75 km s,1. Again, these features do not change with column density, but there are hints that the amplitudes of ,Mg ii(v) and ,Fe ii(v) increase with time. We describe an analytic ,bubble' model for these species, which come from regions that are too compact to be accurately simulated numerically, deriving best-fitting values of Rs, 2.4 Mpc and Ms, 1012 M,. Equally good analytic fits to all four species are found in a similarly biased high-redshift enrichment model in which metals are placed within 2.4 comoving Mpc of Ms, 3 × 109 sources at z= 7.5. [source]


    The temperature of the intergalactic medium and the Compton y parameter

    MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 2 2004
    Pengjie Zhang
    ABSTRACT The thermal Sunyaev,Zeldovich (SZ) effect directly probes the thermal energy of the Universe. Its precision modelling and future high-accuracy measurements will provide a powerful way to constrain the thermal history of the Universe. In this paper, we focus on the precision modelling of the gas density weighted temperature and the mean SZ Compton y parameter. We run high-resolution adiabatic hydrodynamic simulations adopting the WMAP cosmology to study the temperature and density distribution of the intergalactic medium (IGM). To quantify possible simulation limitations, we run n=,1, , 2 self-similar simulations. Our analytical model on is based on energy conservation and matter clustering and has no free parameter. Combining both simulations and analytical models thus provides the precision modelling of and . We find that the simulated temperature probability distribution function and shows good convergence. For the WMAP cosmology, our highest-resolution simulation (10243 cells, 100 Mpc h,1 box size) reliably simulates with better than 10 per cent accuracy for z, 0.5. Toward z= 0, the simulation mass-resolution effect becomes stronger and causes the simulated to be slightly underestimated (at z= 0, ,20 per cent underestimated). Since is mainly contributed by the IGM at z, 0.5, this simulation effect on is no larger than ,10 per cent. Furthermore, our analytical model is capable of correcting this artefact. It passes all tests of self-similar simulations and WMAP simulations and is able to predict and to several per cent accuracy. For a low matter density ,CDM cosmology, the present is 0.32 (,8/0.84)(,m/0.268) keV, which accounts for 10,8 of the critical cosmological density and 0.024 per cent of the cosmic microwave background (CMB) energy. The mean y parameter is 2.6 × 10,6 (,8/0.84)(,m/0.268). The current upper limit of y < 1.5 × 10,5 measured by FIRAS has already ruled out combinations of high ,8, 1.1 and high ,m, 0.5. [source]


    Constraints on the ultraviolet metagalactic emissivity using the Ly, forest

    MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 4 2003
    Avery Meiksin
    ABSTRACT Numerical hydrodynamical simulations have proven a successful means of reproducing many of the statistical properties of the Ly, forest as measured in high redshift quasar spectra. The source of ionization of the intergalactic medium (IGM), however, remains unknown. We investigate how the Ly, forest may be used to probe the nature of the sources. We show that the attenuation of Lyman continuum photons by the IGM depends sensitively on the emissivity of the sources, permitting a strong constraint to be set on the required emissivity to match the measured values of the mean IGM Ly, optical depth. We find that, within the observational errors, quasi-stellar object (QSO) sources alone are able to account for the required ultraviolet (UV) background at z, 4. By contrast, the emissivity of Lyman-break galaxies (LBGs) must decline sharply with redshift, compared with the estimated emissivity at z, 3, so as not to overproduce the UV background and drive the mean Ly, optical depth to values that are too low. We also investigate the effect of fluctuations in the UV background, as would arise if QSOs dominated. To this end, we derive the distribution function of the background radiation field produced by discrete sources in an infinite universe, including the effects of attenuation by an intervening absorbing medium. We show that, for z, 5, the fluctuations significantly boost the mean Ly, optical depth, and so increase the estimate for the mean ionization rate required to match the measured mean Ly, optical depths. The fluctuations will also result in large spatial correlations in the ionization level of the IGM. We show that the large mean Ly, optical depth measured at z, 6 suggests such large correlations will be present if QSOs dominate the UV background. A secondary, smaller effect of the UV background fluctuations is a distortion of the pixel flux distribution. While the effect on the distribution may be too small to detect with existing telescopes, it may be measurable with the extremely large telescopes planned for the future. We also show that if QSOs dominate the UV background at z, 6, then they will be sufficient in number to rejuvenate the ionization of a previously ionized IGM if it has not yet fully recombined. [source]


    Value of the intravenous and oral glucose tolerance tests for detecting subtle impairments in insulin sensitivity and beta-cell function in former gestational diabetes

    CLINICAL ENDOCRINOLOGY, Issue 2 2008
    A. Tura
    Summary Objective, Women with former gestational diabetes mellitus (fGDM) often show defects in both insulin sensitivity and beta-cell function but it is not clear which defect plays the major role or which appears first. This might be because fGDM women are often studied as a unique group and not divided according to their glucose tolerance. Different findings might also be the result of using different tests. Our aim was to study insulin sensitivity and beta-cell function with two independent glucose tolerance tests in fGDM women divided according to their glucose tolerance. Design and patients, A total of 108 fGDM women divided into normal glucose tolerance (IGT; N = 82), impaired glucose metabolism (IGM; N = 20) and overt type 2 diabetes (T2DM; N = 6) groups, and 38 healthy control women (CNT) underwent intravenous (IVGTT) and oral glucose tolerance tests (OGTT). Measurements, Insulin sensitivity and beta-cell function were assessed by both the IVGTT and the OGTT. Results, Both tests revealed impaired insulin sensitivity in the normotolerant group compared to controls (IVGTT: 4·2 ± 0·3 vs. 5·4 ± 0·4 10,4 min,1 (µU/ml),1; OGTT: 440 ± 7 vs. 472 ± 9 ml min,1 m,2). Conversely, no difference was found in beta-cell function from the IVGTT. However, some parameters of beta-cell function by OGTT modelling analysis were found to be impaired: glucose sensitivity (106 ± 5 vs. 124 ± 7 pmol min,1 m,2 mm,1, P = 0·0407) and insulin secretion at 5 mm glucose (168 ± 9 vs. 206 ± 10 pmol min,1 m,2, P = 0·003). Conclusions, Both insulin sensitivity and beta-cell function are impaired in normotolerant fGDM but the subtle defect in beta-cell function is disclosed only by OGTT modelling analysis. [source]


    Human peripheral blood B-cell compartments: A crossroad in B-cell traffic,

    CYTOMETRY, Issue S1 2010
    M. Perez-Andres
    Abstract A relatively high number of different subsets of B-cells are generated through the differentiation of early B-cell precursors into mature B-lymphocytes in the bone marrow (BM) and antigen-triggered maturation of germinal center B-cells into memory B-lymphocytes and plasmablasts in lymphoid tissues. These B-cell subpopulations, which are produced in the BM and lymphoid tissues, recirculate through peripheral blood (PB), into different tissues including mucosa and the BM, where long-living plasma cells produce antibodies. These circulating PB B-cells can be classified according to their maturation stage into i) immature/transitional, ii) naļve, and iii) memory B-lymphocytes, and iv) plasmablasts/plasma cells. Additionally, unique subsets of memory B-lymphocytes and plasmablasts/plasma cells can be identified based on their differential expression of unique Ig-heavy chain isotypes (e.g.: IgM, IgD, IgG, IgA). In the present paper, we review recent data reported in the literature about the distribution, immunophenotypic and functional characteristics of these cell subpopulations, as well as their distribution in PB according to age and seasonal changes. Additional information is also provided in this regard based on the study of a population-based cohort of 600 healthy adults aged from 20 to 80 years, recruited in the Salamanca area in western Spain. Detailed knowledge of the distribution and traffic of B-cell subsets through PB mirrors the immune status of an individual subject and it may also contribute to a better understanding of B-cell disorders related to B-cell biology and homeostasis, such as monoclonal B-cell lymphocytosis (MBL). © 2010 International Clinical Cytometry Society [source]


    Interference in thyroid-stimulating hormone determination

    EUROPEAN JOURNAL OF CLINICAL INVESTIGATION, Issue 8 2010
    Mauro Imperiali
    Eur J Clin Invest 2010; 40 (8): 756,758 Abstract Background, Thyroid-stimulating hormone (TSH) measurement plays a major role in the diagnosis of thyroid disorders. Despite the good quality of immunochemical tests measuring TSH levels, the presence of interfering substances can sometimes alter the TSH results. Design, We reported the case of a 79-year-old man affected by primary autoimmune hypothyroidism hospitalized for pneumonia. A TSH value > 100 mIU L -1 (reference: 0.44 mIU L -1) was found at admission. No signs and symptoms of hypothyroidism were found upon clinical examination and serum concentration of the free thyroxine (FT4) was normal. Results, Serum treatment in heterophile antibody blocking tubes did not change the TSH result in our assay, while normal levels were found in a different immunoassay method. An abnormal pattern was found in protein electrophoresis at admission, with IgG / j and IgM / k monoclonal bands proved in immunofixation. Interestingly, the disappearance of monoclonal bands was paralleled with a normalization of the TSH value. Conclusions, We suggest in this study that the TSH determination might be influenced by the presence of transient paraproteins. [source]


    Aspirin reduces anticardiolipin antibodies in patients with coronary artery disease

    EUROPEAN JOURNAL OF CLINICAL INVESTIGATION, Issue 12 2006
    I. Ikonomidis
    Abstract Background, Anticardiolipin antibodies (aCL) have been found to be elevated in patients with coronary artery disease (CAD) and have been associated with an adverse outcome owing to their prothrombotic activity. The aim of this study was to investigate the effect of aspirin treatment on aCL levels in patients with chronic CAD. Materials and methods, Forty patients with chronic CAD scheduled for elective coronary artery bypass graft surgery (CABG) and 40 healthy controls participated in the study. Patients were treated with 300 mg of aspirin once daily (o.d.) for the first 12 days and placebo for the following 12 days before CABG in a double-blind, cross-over trial. Immunoglobulin (Ig) G-, IgM-, IgA-aCL and C-reactive protein (CRP) levels were measured in the controls and at the end of each treatment period in the patients with CAD. Results, The IgA- and IgG-aCL levels were greater in patients with CAD than in the controls. Compared with the placebo, IgA, IgG subtypes and CRP levels were reduced after aspirin treatment (P = 0·001, P = 0·02, P = 0·04, respectively). The percentage reduction of IgA- and IgG-aCL was related to the percentage reduction of CRP after aspirin (P < 0·05). Conclusion, Aspirin treatment with 300 mg o.d. reduced the serum levels of IgA and IgG subtypes in patients with chronic CAD in parallel to a reduction in CRP. These findings offer an additional pathophysiological mechanism of the beneficial effects of aspirin in patients with chronic CAD. [source]


    IgG2 containing IgM,IgG immune complexes predominate in normal human plasma, but not in plasma of patients with warm autoimmune haemolytic anaemia

    EUROPEAN JOURNAL OF HAEMATOLOGY, Issue 3 2006
    Dorothea Stahl
    Abstract:, The different physicochemical and sterical properties of IgG subclasses may favour a selective enrichment of defined IgG subclasses in IgM,IgG immune complexes (IC) of human plasma under physiological conditions. Such enrichment of IgG subclasses in IgM,IgG IC of plasma may differ from the normal IgG subclass distribution in plasma itself, and contribute to the physiological functions of IgM,IgG IC. Systematic studies on the IgG subclass distribution in IgM,IgG IC in humans are lacking. Using specific analytical techniques to characterise IgM,IgG IC in human plasma (i.e. fast protein liquid chromatography, enzyme-linked immunosorbent assay, affinity biosensor technology), and taking warm autoimmune haemolytic anaemia (WAIHA) of humans as a disease model, we here demonstrate that: (i) IgG2 is the predominant IgG subclass in IgM,IgG IC under physiological conditions, (ii) the predominance of IgG2 within IgM,IgG IC may get lost in polyclonal IgG-mediated autoimmune disease and (iii) the IgG subclass distribution in IgM,IgG IC influences the interaction between IC and blood cells involved in antigen presentation. The data presented here therefore extend the physiological function of IgG2, which is the protective immune response towards carbohydrate antigens in bacterial infections, and suggest IgG2-dependent regulation of immune responses to self-immunoglobulin in humans. The disturbed IgG subclass distribution in IgM,IgG IC of patients with WAIHA might influence activity of self-reactive B cells involved in the pathophysiology of the disease. [source]


    Constitutive activation of Bruton's tyrosine kinase induces the formation of autoreactive IgM plasma cells

    EUROPEAN JOURNAL OF IMMUNOLOGY, Issue 9 2010
    Rogier Kersseboom
    Abstract B-cell receptor (BCR)-mediated signals provide the basis for B-cell differentiation in the BM and subsequently into follicular, marginal zone, or B-1 B-cell subsets. We have previously shown that B-cell-specific expression of the constitutive active E41K mutant of the BCR-associated molecule Bruton's tyrosine kinase (Btk) leads to an almost complete deletion of immature B cells in the BM. Here, we report that low-level expression of the E41K or E41K-Y223F Btk mutants was associated with reduced follicular B-cell numbers and significantly increased proportions of B-1 cells in the spleen. Crosses with 3-83,, and VH81X BCR Tg mice showed that constitutive active Btk expression did not change follicular, marginal zone, or B-1 B-cell fate choice, but resulted in selective expansion or survival of B-1 cells. Residual B cells were hyperresponsive and manifested sustained Ca2+ mobilization. They were spontaneously driven into germinal center-independent plasma cell differentiation, as evidenced by increased numbers of IgM+ plasma cells in spleen and BM and significantly elevated serum IgM. Because anti-nucleosome autoantibodies and glomerular IgM deposition were present, we conclude that constitutive Btk activation causes defective B-cell tolerance, emphasizing that Btk signals are essential for appropriate regulation of B-cell activation. [source]


    Cover Picture , Eur.

    EUROPEAN JOURNAL OF IMMUNOLOGY, Issue 7 2006

    The cover has been specifically designed to introduce the 16th European Congress of Immunology. It combines a picture of the Eiffel Tower with a fluorescence microscopy image of immune cells, underlining the immunological research that will be discussed at the meeting. The immunofluorescence staining shows B lymphocytes (CD45 in red, IgM in blue) forming an immunological synapse with an antigen presenting cell (ICAM-1 in green) and was kindly provided by Yolanda Carrasco, Cancer Research UK, London. [source]


    Specific ICAM-3 grabbing nonintegrin-related 1 (SIGNR1) expressed by marginal zone macrophages is essential for defense against pulmonary Streptococcuspneumoniae infection

    EUROPEAN JOURNAL OF IMMUNOLOGY, Issue 10 2005
    Estella
    Abstract The dendritic cell-specific ICAM-3-grabbing nonintegrin (DC-SIGN) homolog, SIGN-related 1 (SIGNR1) is a pathogen receptor expressed by splenic marginal zone and peritoneal macrophages, and is essential for clearance of Streptococcus pneumoniae by phagocytosis after intraperitoneal infection. Here, we identified an important in vivo function for SIGNR1 in S.pneumonia infection induced via its natural entrance route. Upon intranasal infection with S. pneumoniae, SIGNR1-deficient mice did not clear bacteria from lung and blood, and displayed severely enhanced inflammatory parameters compared to the wild-type mice. However, SIGNR1 is not expressed by alveolar macrophages, suggesting that another mechanism than a decrease in phagocytosis is responsible for this difference. Natural anti-phosphorylcholine IgM produced by marginal zone B cells is essential for protection against infection with S. pneumoniae. Strikingly, during infection, SIGNR1-deficient mice failed to produce a rapid anti-phosphorylcholine IgM response. Marginal zone macrophages have been suggested to capture antigens for presentation to marginal zone B cells. We demonstrate that marginal zone macrophages from SIGNR1-deficient mice in contrast to wild-type mice are not able to capture pneumococci from blood, suggesting that SIGNR1 on marginal zone macrophages captures S. pneumoniae for antigen presentation to and activation of marginal zone B cells, resulting in an anti-phosphorylcholine IgM response. [source]


    Mice with neonatally induced inactivation of the vascular cell adhesion molecule-1 fail to control the parasite in Toxoplasma encephalitis

    EUROPEAN JOURNAL OF IMMUNOLOGY, Issue 5 2003
    Martina Deckert
    Abstract Under various inflammatory conditions, cell adhesion molecules are up-regulated in the central nervous system (CNS) and may contribute to the recruitment of leukocytes to the brain. In the present study, the functional role of vascular cell adhesion molecule (VCAM)-1 in Toxoplasma encephalitis (TE) was addressed using VCAMflox/flox MxCre mice. Neonatal inactivation of the VCAM-1 gene resulted in a lack of induction of VCAM-1 on cerebral blood vessel endothelial cells, whereas the constitutive expression of VCAM-1 on choroid plexus epithelial cells and the ependymawas unaffected; in these animals, resistance to T.,gondii was abolished, and VCAMflox/flox MxCre mice died of chronic TE caused by a failure to control parasites in the CNS. Although leukocyte recruitment to the CNS was unimpaired, the B cell response was significantly reduced as evidenced by reduced serum levels of anti- T.,gondii -specific IgM and IgG antibodies. Furthermore, the frequency and activation state of intracerebral T.,gondii -specific T cells were decreased, and microglial activation was markedly reduced. Taken together, these data demonstrate the crucial requirement of VCAM-1-mediated immune reactions for the control of an intracerebral infectious pathogen, whereas other cell adhesion molecules can efficiently compensate for VCAM-1-mediated homing across cerebral blood vessels. [source]


    Bilateral facial palsy: Epstein,Barr virus, not Lyme disease

    EUROPEAN JOURNAL OF NEUROLOGY, Issue 9 2006
    J. Diedler
    Bilateral facial palsy is frequently linked with lyme disease. We report a patient with bilateral facial palsy due to Epstein-Barr virus infection but with Borrelia burgdorferi IgM in serum caused by polyclonal B-lymphocyte stimulation. [source]


    Modulation of human humoral immune response through orally administered bovine colostrum

    FEMS IMMUNOLOGY & MEDICAL MICROBIOLOGY, Issue 2 2001
    Fang He
    Abstract Eighteen healthy volunteers were randomized into two treatment groups and consumed liquid prepackaged bovine colostrum whey and placebo for 7 days. On days 1, 3 and 5, an attenuated Salmonella typhi Ty21a oral vaccine was given to all subjects to mimic an enteropathogenic infection. The circulating antibody secreting cells and the expression of phagocytosis receptors of the subjects before and after oral immunization were measured with the ELISPOT assay and flow cytometry. All subjects responded well to the vaccine. No significant differences were observed in ELISPOT values for IgA, IgG, IgM, Fc, and CR receptor expression on neutrophils and monocytes between the two groups. There was a trend towards greater increase in specific IgA among the subjects receiving their vaccine with bovine colostrum. These results suggest that bovine colostrum may possess some potential to enhance human special immune responses. [source]


    Human remyelination promoting antibody inhibits apoptotic signaling and differentiation through Lyn kinase in primary rat oligodendrocytes

    GLIA, Issue 15 2010
    J. Watzlawik
    Abstract Purpose: Human remyelination promoting IgM mAbs target oligodendrocytes (OLs) and function in animal models of multiple sclerosis (MS). However, their mechanism of action is unknown. This study seeks to identify the cellular mechanism of action of a recombinant human IgM on OL survival. Methods: Binding of rHIgM22 to the surface of rat OLs was studied by co-localization with various markers. RHIgM22-mediated effects on apoptotic signaling in OLs, differentiation markers, and signaling molecules were detected by Western blotting and immunoprecipitation. Results: RHIgM22 co-localized with integrin ,3 but not other integrin ,-chains in OLs. Downstream of integrin ,3 we identified Src family kinase (SFK) Lyn as a key player of rHIgM22-mediated actions in OLs. Lyn immunoprecipitated in a complex together with integrin ,v,3 and PDGF,R. Lyn expression was 9-fold up-regulated and Lyn activation was 3-fold higher inrHIgM22-treated OL cultures compared with controls. RHIgM22 inhibited apoptotic signaling by greater than 10-fold reduction of caspase-3 and capsase-9 cleavage and reduced by 4-fold expression of differentiation markers MBP and MOG in OLs. SFK inhibitors PP2 and SU6656 inhibited Lyn activity and restored caspase-cleavage in OLs. A human IgM that did not promote remyelination and medium wereused as controls. Conclusions: rHIgM22 prevented apoptotic signaling andinhibited OL differentiation by Lyn implying thatIgM-mediated remyelination is due toprotection of OPC and OLs rather than promotion of OPC differentiation. © 2010 Wiley-Liss, Inc. [source]


    A new ELISA assay for diagnosis of acquired von Willebrand Syndrome

    HAEMOPHILIA, Issue 3 2003
    C. Siaka
    Summary. The pathophysiology of acquired von Willebrand syndrome (AVWS), a rare bleeding disorder, is not fully understood. Circulating antibodies to Von Willebrand factor (VWF) are found in patients with AVWS associated with lymphoproliferative disorders but these autoantibodies are difficult to detect with routine laboratory tests and neutralisation assays. We have developed a simple enzyme-linked immunosorbent assay (ELISA) to detect serum antibody binding to VWF protein immobilized on polystyrene plates. Ten patients with AVWS were studied, eight of whom also had lymphoproliferative disorders. We found antibodies in eight patients; all of them were positive for IgG and five were also positive for IgM. This simple method appears to be more sensitive than functional assays, which failed to identify two of the patients who were positive with the ELISA. In conjunction with other tests, this ELISA method may be useful for demonstrating the immunological mechanism underlying some cases of AVWS. Such patients would qualify for intravenous immunoglobulin therapy, which can correct the clotting disorder. [source]


    Quantitative analysis of anti,hepatitis C virus antibody,secreting B cells in patients with chronic hepatitis C,

    HEPATOLOGY, Issue 1 2006
    Takeji Umemura
    To investigate the quantitative characteristics of humoral immunity in patients with hepatitis C, we established an enzyme-linked immunosorbent spot (ELISpot) assay for detection of anti,hepatitis C virus (HCV)-secreting B cells. Receiver operating characteristic curve analysis demonstrated 100% specificity and 58% to 92% sensitivity for detecting B-cell responses to NS5b, NS3, E2, and core antigens. The median sum of anti-HCV,secreting B cells to all HCV antigens tested was significantly higher in 39 patients with chronic hepatitis C (47.3 spot forming cells [SFCs]/106 peripheral blood mononuclear cells [PBMCs]) than in 9 recovered subjects (15.3 SFCs/106 PBMCs; P = .05) or 11 uninfected controls (5.3 SFCs/106 PBMCs; P < .001); the significant difference (P = .018) in chronic versus recovered patients was in reactivity to nonstructural antigens NS3 and NS5b. Anti-HCV immunoglubulin M (IgM),secreting B cells were also readily detected and persisted decades into HCV infection; there was no difference in IgM-positive cells between chronic and recovered patients. ELISpot reactivity to genotype 1,derived antigens was equivalent in patients of genotypes 1, 2, and 3. There was significant correlation between the numbers of anti-HCV IgG-secreting B cells and serum aminotransferase and to the level of circulating antibody. In conclusion, ELISpot assays can be adapted to study B-cell as well as T-cell responses to HCV. Measurement at the single-cell level suggests that humoral immunity plays a minor role in recovery from HCV infection and that B-cell immunity is strongest in those with persistent infection. (HEPATOLOGY 2005.) [source]


    Major histocompatibility complex (MHC) class II but not MHC class I molecules are required for efficient control of Strongyloides venezuelensis infection in mice

    IMMUNOLOGY, Issue 1pt2 2009
    Rosāngela M. Rodrigues
    Summary Strongyloides stercoralis is an intestinal nematode capable of chronic, persistent infection and hyperinfection of the host; this can lead to dissemination, mainly in immunosuppressive states, in which the infection can become severe and result in the death of the host. In this study, we investigated the immune response against Strongyloides venezuelensis infection in major histocompatibility complex (MHC) class I or class II deficient mice. We found that MHC II,/, animals were more susceptible to S. venezuelensis infection as a result of the presence of an elevated number of eggs in the faeces and a delay in the elimination of adult worms compared with wild-type (WT) and MHC I,/, mice. Histopathological analysis revealed that MHC II,/, mice had a mild inflammatory infiltration in the small intestine with a reduction in tissue eosinophilia. These mice also presented a significantly lower frequency of eosinophils and mononuclear cells in the blood, together with reduced T helper type 2 (Th2) cytokines in small intestine homogenates and sera compared with WT and MHC I,/, animals. Additionally, levels of parasite-specific immunoglobulin M (IgM), IgA, IgE, total IgG and IgG1 were also significantly reduced in the sera of MHC II,/, infected mice, while a non-significant increase in the level of IgG2a was found in comparison to WT or MHC I,/, infected mice. Together, these data demonstrate that expression of MHC class II but not class I molecules is required to induce a predominantly Th2 response and to achieve efficient control of S. venezuelensis infection in mice. [source]


    Roles of proinflammatory cytokines and the Fas/Fas ligand interaction in the pathogenesis of inflammatory myopathies

    IMMUNOLOGY, Issue 1pt2 2009
    Masahiro Kondo
    Summary Within the lesions of inflammatory myopathies, muscle fibres and invading mononuclear cells express Fas and Fas ligand (FasL), respectively. However, the roles of the Fas/FasL interaction in the pathogenesis of inflammatory myopathies are not fully understood. In the present study, we investigated the roles of proinflammatory cytokines and the Fas/FasL system in the pathogenesis of inflammatory myopathies. In vitro culturing of muscle cells with the proinflammatory cytokines interferon-,, tumour necrosis factor-,, and interleukin (IL)-1, synergistically increased Fas expression, susceptibility to Fas-mediated apoptosis, and the expression of cytoplasmic caspases 8 and 3. In addition, culturing of muscle cells with activated CD4+ T cells induced muscle cell apoptosis, which was partially inhibited by anti-FasL antibody. We also tested the possibility that T helper (Th) 17, which is an IL-17-producing helper T-cell subset that plays crucial roles in autoimmune and inflammatory responses, participates in the pathogenesis of inflammatory myopathies. Interestingly, in vitro culturing of dendritic cells with anti-Fas immunoglobulin M (IgM) or activated CD4+ T cells induced the expression of mRNA for IL-23p19, but not for IL-12p35, in addition to proinflammatory cytokines. Furthermore, IL-23p19 and IL-17 mRNAs were detected in the majority of biopsy samples from patients with inflammatory myopathies. Taken together, these results suggest that proinflammatory cytokines enhance Fas-mediated apoptosis of muscle cells, and that the Fas/FasL interaction between invading dendritic cells and CD4+ T cells induces local production of IL-23 and proinflammatory cytokines, which can promote the proliferation of Th17 cells and enhance Fas-mediated apoptosis of muscle cells, respectively. [source]