267 research outputs found
Uptake and turnover of mono-iodinated thyroid hormone metabolites by PCCL3 thyrocytes
Tyrosine and phenolic ring de-iodination of thyroid hormones (TH) is crucial
for regulating their physiological activity. Furthermore, reactions such as
de-carboxylation to thyronamines (TAM) and de-amination to thyroacetic acids
(TAc) produce TH metabolites (THM) with distinct biological properties. This
needs to be considered when studying effects of TH and THM. The accurate and
precise quantitative analysis of TH and THM in cell culture supernatants and
cell lysates are key procedures required for studying the in vitro metabolism
of TH. We report here the development of a liquid-liquid extraction/isotope
dilution-liquid chromatography-electrospray tandem mass spectrometry (LC-
MS/MS) method for the quantification of 9 thyronines (TN) and 6 TAM in human
hepatocellular carcinoma Hep G2 cell lysate extracts. In addition, we adapted
the method to quantify TH, TAM and TAc, in cell lysates of FBS-depleted rat
thyroid epithelium PCCL3 cells. The methods for both cell lines were validated
by rigorous assessment of linearity, limits of quantification and detection
(LLOQ and LLOD respectively), intra- and inter-day accuracy, precision,
process efficiency (PE), matrix effect (ME) and relative recovery (RE).
Calibration curves covering 11 concentrations (based on 400 μl of lysate) were
linear in the range 0.016–50 nM and 0.010–50 nM for Hep G2 and PCCL3 cells
respectively. The lower limits of quantification were in the range 0.031 to 1
nM. We applied the PCCL3 version of the LC-MS/MS method to the analysis of
lysed cell extracts from PCCL3 cells that had been incubated with
3-iodo-L-thyronine (T1), 3-iodothyronamine (3-T1AM) and 3-iodothyroacetic acid
(3-T1Ac). Over the course of 30 minutes incubation 3-T1AM was de-iodinated to
4-[4-(2-aminoethylphenoxy)]phenol (thyronamine, T0AM) and de-aminated to
3-T1Ac respectively, whilst T1 underwent de-iodination to T0. This data
indicates avid metabolism of these mono-iodinated compounds and the utility of
LC-MS/MS to quantify such cellular metabolism
The Calogero-Moser equation system and the ensemble average in the Gaussian ensembles
From random matrix theory it is known that for special values of the coupling
constant the Calogero-Moser (CM) equation system is nothing but the radial part
of a generalized harmonic oscillator Schroedinger equation. This allows an
immediate construction of the solutions by means of a Rodriguez relation. The
results are easily generalized to arbitrary values of the coupling constant. By
this the CM equations become nearly trivial.
As an application an expansion for in terms of eigenfunctions of
the CM equation system is obtained, where X and Y are matrices taken from one
of the Gaussian ensembles, and the brackets denote an average over the angular
variables.Comment: accepted by J. Phys.
Impurity effects on the band structure of one-dimensional photonic crystals: Experiment and theory
We study the effects of single impurities on the transmission in microwave
realizations of the photonic Kronig-Penney model, consisting of arrays of
Teflon pieces alternating with air spacings in a microwave guide. As only the
first propagating mode is considered, the system is essentially one dimensional
obeying the Helmholtz equation. We derive analytical closed form expressions
from which the band structure, frequency of defect modes, and band profiles can
be determined. These agree very well with experimental data for all types of
single defects considered (e.g. interstitial, substitutional) and shows that
our experimental set-up serves to explore some of the phenomena occurring in
more sophisticated experiments. Conversely, based on the understanding provided
by our formulas, information about the unknown impurity can be determined by
simply observing certain features in the experimental data for the
transmission. Further, our results are directly applicable to the closely
related quantum 1D Kronig-Penney model.Comment: 16 pages, 7 figure
Geometry-dependent scattering through quantum billiards: Experiment and theory
We present experimental studies of the geometry-specific quantum scattering
in microwave billiards of a given shape. We perform full quantum mechanical
scattering calculations and find an excellent agreement with the experimental
results. We also carry out the semiclassical calculations where the conductance
is given as a sum of all classical trajectories between the leads, each of them
carrying the quantum-mechanical phase. We unambiguously demonstrate that the
characteristic frequencies of the oscillations in the transmission and
reflection amplitudes are related to the length distribution of the classical
trajectories between the leads, whereas the frequencies of the probabilities
can be understood in terms of the length difference distribution in the pairs
of classical trajectories. We also discuss the effect of non-classical "ghost"
trajectories that include classically forbidden reflection off the lead mouths.Comment: 4 pages, 4 figure
Pressure-sensitive paint measurements in a shock tube
Abstract Surface pressures were measured in the shortduration, transient flow environment of a small-scale, low pressure-ratio shock tube using thin-film pressure-sensitive paint (PSP). Issues regarding coating formulation, measurement uncertainty, optical system design, and temperature and illumination compensation are discussed. The pressure measurements were acquired during steady flow conditions following the passage of normal shocks and expansion regions along a flat sidewall and a wedge sidewall. The PSP characteristic response time was 3 to 6 ms. Overall pressure uncertainty for the shock tube measurements ranged up to 5% over one atmosphere and compared well with theoretical estimates of uncertainty
Corrigendum: Valenced action/inhibition learning in humans is modulated by a genetic variant linked to dopamine D2 receptor expression
Motivational salience plays an important role in shaping human behavior, but recent studies demonstrate that human performance is not uniformly improved by motivation. Instead, action has been shown to dominate valence in motivated tasks, and it is particularly difficult for humans to learn the inhibition of an action to obtain a reward, but the neural mechanism behind this behavioral specificity is yet unclear. In all mammals, including humans, the monoamine neurotransmitter dopamine is particularly important in the neural manifestation of appetitively motivated behavior, and the human dopamine system is subject to considerable genetic variability. The well-studied TaqIA restriction fragment length polymorphism (rs1800497) has previously been shown to affect striatal dopamine metabolism. In this study we investigated a potential effect of this genetic variation on motivated action/inhibition learning. Two independent cohorts consisting of 87 and 95 healthy participants, respectively, were tested using the previously described valenced go/no-go learning paradigm in which participants learned the reward-associated no-go condition significantly worse than all other conditions. This effect was modulated by the TaqIA polymorphism, with carriers of the A1 allele showing a diminished learning-related performance enhancement in the rewarded no-go condition compared to the A2 homozygotes. This result highlights a modulatory role for genetic variability of the dopaminergic system in individual learning differences of action-valence interaction
Green functions for generalized point interactions in 1D: A scattering approach
Recently, general point interactions in one dimension has been used to model
a large number of different phenomena in quantum mechanics. Such potentials,
however, requires some sort of regularization to lead to meaningful results.
The usual ways to do so rely on technicalities which may hide important
physical aspects of the problem. In this work we present a new method to
calculate the exact Green functions for general point interactions in 1D. Our
approach differs from previous ones because it is based only on physical
quantities, namely, the scattering coefficients, and , to construct .
Renormalization or particular mathematical prescriptions are not invoked. The
simple formulation of the method makes it easy to extend to more general
contexts, such as for lattices of general point interactions; on a line; on
a half-line; under periodic boundary conditions; and confined in a box.Comment: Revtex, 9 pages, 3 EPS figures. To be published in PR
NEMF mutations that impair ribosome-associated quality control are associated with neuromuscular disease
A hallmark of neurodegeneration is defective protein quality control. The E3 ligase Listerin (LTN1/Ltn1) acts in a specialized protein quality control pathway—Ribosome-associated Quality Control (RQC)—by mediating proteolytic targeting of incomplete polypeptides produced by ribosome stalling, and Ltn1 mutation leads to neurodegeneration in mice. Whether neurodegeneration results from defective RQC and whether defective RQC contributes to human disease have remained unknown. Here we show that three independently-generated mouse models with mutations in a different component of the RQC complex, NEMF/Rqc2, develop progressive motor neuron degeneration. Equivalent mutations in yeast Rqc2 selectively interfere with its ability to modify aberrant translation products with C-terminal tails which assist with RQC-mediated protein degradation, suggesting a pathomechanism. Finally, we identify NEMF mutations expected to interfere with function in patients from seven families presenting juvenile neuromuscular disease. These uncover NEMF’s role in translational homeostasis in the nervous system and implicate RQC dysfunction in causing neurodegeneration
Evaluación del riesgo de inundación a múltiples componentes en la costa del Maresme
The coast is one of the areas most affected by natural hazards, with floods being the most frequent and significant of these in terms of their induced impacts, so any management scheme requires their evaluation. In coastal areas, flooding is a hazard associated with different processes acting at different scales: coastal storms, flash floods and sea level rise (SLR). To address the problem as a whole, this study presents a methodology to undertake a preliminary integrated risk assessment of the magnitude of each flood component, taking into account their scope (extension of the affected area) and their temporal scale. The risk is quantified using specific indicators to assess the hazard magnitude (for each component) and the consequences. This allows for a robust comparison of the spatial risk distribution along the coast in order to identify both the most at-risk areas and the most influential risk components. This methodology is applied to a stretch of coastline (Maresme, Catalonia) representative of the Spanish Mediterranean coast. The results obtained characterise this coastline as an area with a relatively low overall risk, although some hotspots are identified as having high-risk values. Resumen: La costa es una de las zonas más sometidas a riesgos naturales, siendo la inundación uno de los más frecuentes e importantes en términos de daños inducidos, por lo que cualquier esquema de gestión requiere evaluación. La inundación en zonas costeras es una amenaza natural asociada a diferentes procesos que actúan a distintas escalas: tormentas costeras, riadas y subida del nivel del mar (SNM). Para abarcar la totalidad del problema, este trabajo propone una metodologÃa para la evaluación preliminar del riesgo integrado de inundación costera a una escala regional que permite evaluar la magnitud de cada componente teniendo en cuenta su alcance (extensión de la zona afectada) y su escala temporal. El riesgo se cuantifica en función de unos indicadores especÃficos que valoran la magnitud de la amenaza para cada componente y las consecuencias. Esto permite comparar robustamente la distribución espacial del riesgo a lo largo de la costa, para identificar tanto zonas de mayor riesgo como las componentes que más contribuyen al mismo. Aplicamos esta metodologÃa a un tramo de costa caracterÃstica del Mediterráneo español (Maresme, Cataluña). Los resultados permiten caracterizar esta costa como un área con un riesgo global relativamente bajo, pero algunos puntos singulares con riesgo alto
Four minutes for a patient, twenty seconds for a relative - an observational study at a university hospital
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