182 research outputs found
The Solution Structures of Two Human IgG1 Antibodies Show Conformational Stability and Accommodate Their C1q and FcγR Ligands.
The human IgG1 antibody subclass shows distinct properties compared with the IgG2, IgG3, and IgG4 subclasses and is the most exploited subclass in therapeutic antibodies. It is the most abundant subclass, has a half-life as long as that of IgG2 and IgG4, binds the FcγR receptor, and activates complement. There is limited structural information on full-length human IgG1 because of the challenges of crystallization. To rectify this, we have studied the solution structures of two human IgG1 6a and 19a monoclonal antibodies in different buffers at different temperatures. Analytical ultracentrifugation showed that both antibodies were predominantly monomeric, with sedimentation coefficients s20,w (0) of 6.3-6.4 S. Only a minor dimer peak was observed, and the amount was not dependent on buffer conditions. Solution scattering showed that the x-ray radius of gyration Rg increased with salt concentration, whereas the neutron Rg values remained unchanged with temperature. The x-ray and neutron distance distribution curves P(r) revealed two peaks, M1 and M2, whose positions were unchanged in different buffers to indicate conformational stability. Constrained atomistic scattering modeling revealed predominantly asymmetric solution structures for both antibodies with extended hinge structures. Both structures were similar to the only known crystal structure of full-length human IgG1. The Fab conformations in both structures were suitably positioned to permit the Fc region to bind readily to its FcγR and C1q ligands without steric clashes, unlike human IgG4. Our molecular models for human IgG1 explain its immune activities, and we discuss its stability and function for therapeutic applications
Cosmoglobe DR1. III. First full-sky model of polarized synchrotron emission from all WMAP and Planck LFI data
We present the first model of full-sky polarized synchrotron emission that is
derived from all WMAP and Planck LFI frequency maps. The basis of this analysis
is the set of end-to-end reprocessed Cosmoglobe Data Release 1 sky maps
presented in a companion paper, which have significantly lower instrumental
systematics than the legacy products from each experiment. We find that the
resulting polarized synchrotron amplitude map has an average noise rms of
at 30 GHz and FWHM, which is 30% lower than
the recently released BeyondPlanck model that included only LFI+WMAP Ka-V data,
and 29% lower than the WMAP K-band map alone. The mean -to- power
spectrum ratio is , with amplitudes consistent with those measured
previously by Planck and QUIJOTE. Assuming a power law model for the
synchrotron spectral energy distribution, and using the -- plot method,
we find a full-sky inverse noise-variance weighted mean of
between Cosmoglobe DR1 K-band and 30 GHz, in
good agreement with previous estimates. In summary, the novel Cosmoglobe DR1
synchrotron model is both more sensitive and systematically cleaner than
similar previous models, and it has a more complete error description that is
defined by a set of Monte Carlo posterior samples. We believe that these
products are preferable over previous Planck and WMAP products for all
synchrotron-related scientific applications, including simulation, forecasting
and component separation.Comment: 15 pages, 15 figures, submitted to A&
Molecular and functional interactions between tumor necrosis factor-alpha receptors and the glutamatergic system in the mouse hippocampus : implications for seizure susceptibility
Tumor necrosis factor (TNF)-alpha is a proinflammatory cytokine acting on two distinct receptor subtypes, namely p55 and p75 receptors. TNF-alpha p55 and p75 receptor knockout mice were previously shown to display a decreased or enhanced susceptibility to seizures, respectively, suggesting intrinsic modifications in neuronal excitability. We investigated whether alterations in glutamate system function occur in these naive knockout mice with perturbed cytokine signaling that could explain their different propensity to develop seizures. Using Western blot analysis of hippocampal homogenates, we found that p55(-/-) mice have decreased levels of membrane GluR3 and NR1 glutamate receptor subunits while GluR1, GluR2, GluR6/7 and NR2A/B were unchanged as compared to wild-type mice. In p75(-/-) mice, GluR2, GluR3, GluR6/7 and NR2A/B glutamate receptor subunits were increased in the hippocampus while GluR1 and NR1 did not change. Extracellular single-cell recordings of the electrical activity of hippocampal neurons were carried out in anesthetized mice by standard electrophysiological techniques. Microiontophoretic application of glutamate increased the basal firing rate of hippocampal neurons in p75(-/-) mice versus wild-type mice, and this effect was blocked by 2-amino-5-phosphopentanoic acid and 6-nitro-7-sulfamoyl-benzo(f)quinoxaline-2,3-dione denoting the involvement of N-methyl-D-aspartic acid and AMPA receptors. In p55(-/-) mice, hippocampal neurons responses to glutamate were similar to wild-type mice. Spontaneous glutamate release measured by in vivo hippocampal microdialysis was significantly decreased only in p55(-/-) mice. No changes were observed in KCl-induced glutamate release in both receptor knockout mice strains versus wild-type mice. These findings highlight specific molecular and functional interactions between p55 and p75 receptor-mediated signaling and the glutamate system. These interactions may be relevant for controlling neuronal excitability in physiological and pathological conditions.peer-reviewe
Signal transduction pathways involved in proteolysis-inducing factor induced proteasome expression in murine myotubes
The proteolysis-inducing factor (PIF) is produced by cachexia-inducing tumours and initiates protein catabolism in skeletal muscle. The potential signalling pathways linking the release of arachidonic acid (AA) from membrane phospholipids with increased expression of the ubiquitin-proteasome proteolytic pathway by PIF has been studied using C2C12 murine myotubes as a surrogate model of skeletal muscle. The induction of proteasome activity and protein degradation by PIF was blocked by quinacrine, a nonspecific phospholipase A2 (PLA2) inhibitor and trifluroacetyl AA, an inhibitor of cytosolic PLA2. PIF was shown to increase the expression of calcium-independent cytosolic PLA2, determined by Western blotting, at the same concentrations as those inducing maximal expression of 20S proteasome α-subunits and protein degradation. In addition, both U-73122, which inhibits agonist-induced phospholipase C (PLC) activation and D609, a specific inhibitor of phosphatidylcholine-specific PLC also inhibited PIF-induced proteasome activity. This suggests that both PLA 2 and PLC are involved in the release of AA in response to PIF, and that this is important in the induction of proteasome expression. The two tyrosine kinase inhibitors genistein and tryphostin A23 also attenuated PIF-induced proteasome expression, implicating tyrosine kinase in this process. PIF induced phosphorylation of p44/42 mitogen-activated protein kinase (MAPK) at the same concentrations as that inducing proteasome expression, and the effect was blocked by PD98059, an inhibitor of MAPK kinase, as was also the induction of proteasome expression, suggesting a role for MAPK activation in PIF-induced proteasome expression. © 2003 Cancer Research UK
BeyondPlanck II. CMB map-making through Gibbs sampling
We present a Gibbs sampling solution to the map-making problem for CMB
measurements, building on existing destriping methodology. Gibbs sampling
breaks the computationally heavy destriping problem into two separate steps;
noise filtering and map binning. Considered as two separate steps, both are
computationally much cheaper than solving the combined problem. This provides a
huge performance benefit as compared to traditional methods, and allows us for
the first time to bring the destriping baseline length to a single sample. We
apply the Gibbs procedure to simulated Planck 30 GHz data. We find that gaps in
the time-ordered data are handled efficiently by filling them with simulated
noise as part of the Gibbs process. The Gibbs procedure yields a chain of map
samples, from which we may compute the posterior mean as a best-estimate map.
The variation in the chain provides information on the correlated residual
noise, without need to construct a full noise covariance matrix. However, if
only a single maximum-likelihood frequency map estimate is required, we find
that traditional conjugate gradient solvers converge much faster than a Gibbs
sampler in terms of total number of iterations. The conceptual advantages of
the Gibbs sampling approach lies in statistically well-defined error
propagation and systematic error correction, and this methodology forms the
conceptual basis for the map-making algorithm employed in the BeyondPlanck
framework, which implements the first end-to-end Bayesian analysis pipeline for
CMB observations.Comment: 11 pages, 10 figures. All BeyondPlanck products and software will be
released publicly at http://beyondplanck.science during the online release
conference (November 18-20, 2020). Connection details will be made available
at the same website. Registration is mandatory for the online tutorial, but
optional for the conferenc
BeyondPlanck VII. Bayesian estimation of gain and absolute calibration for CMB experiments
We present a Bayesian calibration algorithm for CMB observations as
implemented within the global end-to-end BeyondPlanck (BP) framework, and apply
this to the Planck Low Frequency Instrument (LFI) data. Following the most
recent Planck analysis, we decompose the full time-dependent gain into a sum of
three orthogonal components: One absolute calibration term, common to all
detectors; one time-independent term that can vary between detectors; and one
time-dependent component that is allowed to vary between one-hour pointing
periods. Each term is then sampled conditionally on all other parameters in the
global signal model through Gibbs sampling. The absolute calibration is sampled
using only the orbital dipole as a reference source, while the two relative
gain components are sampled using the full sky signal, including the orbital
and Solar CMB dipoles, CMB fluctuations, and foreground contributions. We
discuss various aspects of the data that influence gain estimation, including
the dipole/polarization quadrupole degeneracy and anomalous jumps in the
instrumental gain. Comparing our solution to previous pipelines, we find good
agreement in general, with relative deviations of -0.84% (-0.67%) for 30 GHz,
-0.14% (0.02%) for 44 GHz and -0.69% (-0.08%) for 70 GHz, compared to Planck
2018 (NPIPE). The deviations we find are within expected error bounds, and we
attribute them to differences in data usage and general approach between the
pipelines. In particular, the BP calibration is performed globally, resulting
in better inter-frequency consistency. Additionally, WMAP observations are used
actively in the BP analysis, which breaks degeneracies in the Planck data set
and results in better agreement with WMAP. Although our presentation and
algorithm are currently oriented toward LFI processing, the procedure is fully
generalizable to other experiments.Comment: 18 pages, 15 figures. All BeyondPlanck products and software will be
released publicly at http://beyondplanck.science during the online release
conference (November 18-20, 2020). Connection details will be made available
at the same website. Registration is mandatory for the online tutorial, but
optional for the conferenc
BeyondPlanck XII. Cosmological parameter constraints with end-to-end error propagation
We present cosmological parameter constraints as estimated using the Bayesian
BeyondPlanck (BP) analysis framework. This method supports seamless end-to-end
error propagation from raw time-ordered data to final cosmological parameters.
As a first demonstration of the method, we analyze time-ordered Planck LFI
observations, combined with selected external data (WMAP 33-61GHz, Planck HFI
DR4 353 and 857GHz, and Haslam 408MHz) in the form of pixelized maps which are
used to break critical astrophysical degeneracies. Overall, all results are
generally in good agreement with previously reported values from Planck 2018
and WMAP, with the largest relative difference for any parameter of about 1
sigma when considering only temperature multipoles between 29<l<601. In cases
where there are differences, we note that the BP results are generally slightly
closer to the high-l HFI-dominated Planck 2018 results than previous analyses,
suggesting slightly less tension between low and high multipoles. Using low-l
polarization information from LFI and WMAP, we find a best-fit value of
tau=0.066 +/- 0.013, which is higher than the low value of tau=0.051 +/- 0.006
derived from Planck 2018 and slightly lower than the value of 0.069 +/- 0.011
derived from joint analysis of official LFI and WMAP products. Most
importantly, however, we find that the uncertainty derived in the BP processing
is about 30% larger than when analyzing the official products, after taking
into account the different sky coverage. We argue that this is due to
marginalizing over a more complete model of instrumental and astrophysical
parameters, and this results in both more reliable and more rigorously defined
uncertainties. We find that about 2000 Monte Carlo samples are required to
achieve robust convergence for low-resolution CMB covariance matrix with 225
independent modes.Comment: 13 pages, 10 figure
BeyondPlanck XIV. Polarized foreground emission between 30 and 70GHz
We constrain polarized foreground emission between 30 and 70GHz with the
Planck Low Frequency Instrument (LFI) and WMAP data within the framework of
BeyondPlanck global Bayesian analysis. We combine for the first time
full-resolution Planck LFI time-ordered data with low-resolution WMAP sky maps
at 33, 40 and 61GHz. Spectral parameters are fit with a likelihood defined at
the native resolution of each frequency channel. This analysis represents the
first implementation of true multi-resolution component separation applied to
CMB observations for both amplitude and spectral energy distribution (SED)
parameters. For synchrotron emission, we approximate the SED as a power-law in
frequency and find that the low signal-to-noise ratio of the data set strongly
limits the number of free parameters that may be robustly constrained. We
partition the sky into four large disjoint regions (High Latitude; Galactic
Spur; Galactic Plane; and Galactic Center), each associated with its own
power-law index. We find that the High Latitude region is prior-dominated,
while the Galactic Center region is contaminated by residual instrumental
systematics. The two remaining regions appear to be both signal-dominated and
clean of systematics, and for these we derive spectral indices of
and . This agrees qualitatively with the WMAP-only
polarization constraints presented by Dunkley et al. (2009), but contrasts with
several temperature-based analyses. For thermal dust emission we assume a
modified blackbody model and we fit the power-law index across the full sky. We
find , which is slightly steeper than that
previously reported from Planck HFI data, but still statistically consistent at
a 2 confidence level.Comment: 17 pages, 14 figures. All BeyondPlanck products and software will be
released publicly at http://beyondplanck.science during the online release
conference (November 18-20, 2020). Connection details will be made available
at the same website. Registration is mandatory for the online tutorial, but
optional for the conferenc
Bone Mass and Strength in Older Men With Type 2 Diabetes: The Osteoporotic Fractures in Men Study
The effects of type 2 diabetes mellitus (T2DM) on bone volumetric density, bone geometry, and estimates of bone strength are not well established. We used peripheral quantitative computed tomography (pQCT) to compare tibial and radial bone volumetric density (vBMD, mg/cm3), total (ToA, mm2) and cortical (CoA, mm2) bone area and estimates of bone compressive and bending strength in a subset (n = 1171) of men (≥65 years of age) who participated in the multisite Osteoporotic Fractures in Men (MrOS) study. Analysis of covariance–adjusted bone data for clinic site, age, and limb length (model 1) and further adjusted for body weight (model 2) were used to compare data between participants with (n = 190) and without (n = 981) T2DM. At both the distal tibia and radius, patients with T2DM had greater bone vBMD (+2% to +4%, model 1, p < .05) and a smaller bone area (ToA −1% to −4%, model 2, p < .05). The higher vBMD compensated for lower bone area, resulting in no differences in estimated compressive bone strength at the distal trabecular bone regions. At the mostly cortical bone midshaft sites of the radius and tibia, men with T2DM had lower ToA (−1% to −3%, p < .05), resulting in lower bone bending strength at both sites after adjusting for body weight (−2% to −5%, p < .05) despite the lack of difference in cortical vBMD at these sites. These data demonstrate that older men with T2DM have bone strength that is low relative to body weight at the cortical-rich midshaft of the radius despite no difference in cortical vBMD. © 2010 American Society for Bone and Mineral Researc
Cosmoglobe DR1 results. II. Constraints on isotropic cosmic birefringence from reprocessed WMAP and Planck LFI data
Cosmic birefringence is a parity-violating effect that might have rotated the
plane of linearly polarized light of the cosmic microwave background (CMB) by
an angle since its emission. This has recently been measured to be
non-zero at a statistical significance of in the official Planck
PR4 and 9-year WMAP data. In this work, we constrain using the
reprocessed BeyondPlanck LFI and Cosmoglobe DR1 WMAP polarization maps. These
novel maps have both lower systematic residuals and a more complete error
description than the corresponding official products. Foreground
correlations could bias measurements of , and while thermal dust
emission has been argued to be statistically non-zero, no evidence for
synchrotron power has been reported. Unlike the dust-dominated Planck HFI
maps, the majority of the LFI and WMAP polarization maps are instead dominated
by synchrotron emission. Simultaneously constraining and the
polarization miscalibration angle, , of each channel, we find a
best-fit value of with LFI and WMAP data
only. When including the Planck HFI PR4 maps, but fitting separately
for dust-dominated, , and synchrotron-dominated
channels, , we find . This differs from zero with a
statistical significance of , and the main contribution to this
value comes from the LFI 70 GHz channel. While the statistical significances of
these results are low on their own, the measurement derived from the LFI and
WMAP synchrotron-dominated maps agrees with the previously reported
HFI-dominated constraints, despite the very different astrophysical and
instrumental systematics involved in all these experiments.Comment: 10 pages, 7 figures, 2 tables. Submitted to A&
- …