| 1. |
- Darreh-Shori, T, et al.
(författare)
-
The apolipoprotein E varepsilon4 allele plays pathological roles in AD through high protein expression and interaction with butyrylcholinesterase.
- 2011
-
Ingår i: Neurobiology of aging. - : Elsevier BV. - 1558-1497 .- 0197-4580. ; 32:7, s. 1236-48
-
Tidskriftsartikel (refereegranskat)abstract
- The apolipoprotein E (ApoE) varepsilon4 allele has consistently been established as an Alzheimer's disease (AD) risk factor, but its pathological contribution to AD is obscure. Certain butyrylcholinesterase (BuChE) polymorphisms together with the ApoE varepsilon4 allele synergistically increase the risk of AD. In addition, AD risk factors, i.e. advanced age, female gender and ApoE varepsilon4 are associated with different levels of CSF BuChE in AD patients, and BuChE protein attenuates Abeta fibrillization in vitro. Here we investigated the roles of ApoE and BuChE gene products as modulators of pathological features of AD in vivo. We found that AD risk factors were associated with different levels of ApoE protein in the CSF of AD patients (n=115). Women and ApoE varepsilon4 carriers had the highest levels of ApoE protein (up by 50-120%, p<0.01-0.0001), which were increased with age (r=0.30, p<0.0006). The CSF surrogate markers of pathological features of AD, i.e. high tau and P-tau, low Abeta(42) and high tau/Abeta(42) ratio, were associated with high levels of ApoE protein. Intriguingly, high ApoE protein levels were not only associated with low amounts of BuChE, but they also altered the aging and activity of this enzyme in concentration- and isoform-dependent manners, particularly in the presence of Abeta peptides. Both ApoE and BuChE levels were also differentially related to levels of the proinflammatory cytokine IL-1beta. In conclusion, ApoE varepsilon4 might impart its pathological role through high protein expression and interaction with BuChE, which in turn might modulate central cholinergic activity and Abeta load in the brain.
|
|
| 2. |
- Jaron, Frédéric, et al.
(författare)
-
Cross-Polarization Gain Calibration of Linearly Polarized VLBI Antennas by Observations of 4C 39.25
- 2024
-
Ingår i: Radio Science. - 0048-6604 .- 1944-799X. ; 59:4
-
Tidskriftsartikel (refereegranskat)abstract
- Radio telescopes with dual linearly polarized feeds regularly participate in Very Long Baseline Interferometry. One example is the VLBI Global Observing System (VGOS), which is employed for high-precision geodesy and astrometry. In order to achieve the maximum signal-to-noise ratio, the visibilities of all four polarization products are combined to Stokes I before fringe-fitting. Our aim is to improve cross-polarization bandpass calibration, which is an essential processing step in this context. Here we investigate the shapes of these station-specific quantities as a function of frequency and time. We observed the extra-galactic source 4C 39.25 for 6 hours with a VGOS network. We correlated the data with the DiFX software and analyzed the visibilities with PolConvert to determine the complex cross-bandpasses with high accuracy. Their frequency-dependent shape is to first order characterized by a group delay between the two orthogonal polarizations, in the order of several hundred picoseconds. We find that this group delay shows systematic variability in the range of a few picoseconds, but can remain stable within this range for several years, as evident from earlier sessions. On top of the linear phase-frequency relationship there are systematic deviations of several tens of degrees, which in addition are subject to smooth temporal evolution. The antenna cross-bandpasses are variable on time scales of ∼1 hr, which defines the frequency of necessary calibrator scans. The source 4C 39.25 is confirmed as an excellent cross-bandpass calibrator. Dedicated surveys are highly encouraged to search for more calibrators of similar quality.
|
|
