8,665 research outputs found
Regulation of transforming growth factor-beta 1 gene expression by glucocorticoids in normal human T lymphocytes.
Glucocorticoids (GC) modulate immune function in a number of ways, including suppression of T cell proliferation and other IL-2-mediated T cell functions. These inhibitory effects are similar to those induced by transforming growth factor-beta 1 (TGF-beta 1), a cytokine with potent T cell inhibiting activities. We examined the hypothesis that GC effects may be at least partially achieved through modulation of the expression of the TGF-beta 1 gene in activated T cells. Normal T cells were cultured with or without purified phytohemagglutinin (PHA-p) and 4 beta-phorbol 12-myristate 13-acetate (PMA) in the presence or absence of the synthetic GC, dexamethasone (100-200 micrograms/ml). The production of latent and active forms of TGF beta by these cells were analyzed by immunoblotting and bioassays. The steady-state levels of TGF-beta 1 mRNA were analyzed in total RNA from these cells by Northern hybridizations using a human TGF-beta 1 cDNA. The results showed that dexamethasone caused an increase in TGF beta production and a dose-dependent two to fourfold increase in TGF-beta 1 mRNA in activated as well as in unstimulated T cells, 1 h after exposure of the cultures to the steroid. The increase in TGF-beta 1 mRNA levels by dexamethasone was further potentiated two to threefold by cycloheximide, suggesting that the steroid effect may be due to inhibition of the synthesis of proteins that decrease TGF-beta 1 gene transcription or the stability of its transcripts. Finally, in vitro nuclear transcription studies indicated the dexamethasone effects on TGF-beta 1 gene expression to be largely transcriptional
Circulating anti-galectin-1 antibodies are associated with the severity of ocular disease in autoimmune and infectious uveitis
Galectin (Gal)-1, an endogenous lectin found at sites of immune privilege, plays a critical role in the regulation of the immune response. Therapeutic administration of Gal-1 or its genetic delivery suppresses chronic inflammation in experimental models of autoimmunity. The purpose of this work was to investigate the occurrence of circulating anti-Gal-1 antibodies in patients with autoimmune and infectious uveitis as potential determinant factors of disease progression.Fil: Romero, Marta D.. Universidad de Buenos Aires. Facultad de Medicina; Argentina. Fundación Ver; Argentina. Laboratorio Inmunopatología Investigación y Docencia LIIDO; ArgentinaFil: Muiño, Juan Carlos. Universidad Nacional de Córdoba; Argentina. Fundación Ver; ArgentinaFil: Bianco, German Ariel. Universidad de Buenos Aires. Facultad de Medicina; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Biología y Medicina Experimental. Fundación de Instituto de Biología y Medicina Experimental. Instituto de Biología y Medicina Experimental; ArgentinaFil: Ferrero, Mercedes. Laboratorio Inmunopatología Investigación y Docencia LIIDO; Argentina. Fundación Ver; ArgentinaFil: Juarez, Claudio P.. Fundación Ver; ArgentinaFil: Luna, José Domingo. Fundación Ver; ArgentinaFil: Rabinovich, Gabriel A.. Universidad de Buenos Aires. Facultad de Medicina; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Biología y Medicina Experimental. Fundación de Instituto de Biología y Medicina Experimental. Instituto de Biología y Medicina Experimental; Argentin
A spectroscopic survey of the youngest field stars in the solar neighbourhood. I. The optically bright sample
We present the first results of a ground-based programme conducted on 1-4m
class telescopes. Our sample consists of 1097 active and presumably young
stars, all of them being optical counterparts of RASS X-ray sources in the
northern hemisphere. We concentrate on the 704 optically brightest
(V_Ticho<=9.5 mag) candidates. We acquired high-res spectroscopy in the
Halpha/Li spectral regions for 426 of such stars without relevant literature
data. We describe the sample and the observations and we start to discuss its
physical properties. We used a cross-correlation technique and other tools to
derive accurate radial/rotational velocities and to perform a spectral
classification for both single and SB2 stars. The spectral subtraction
technique was used to derive chromospheric activity levels and Li abundances.
We estimated the fraction of young single stars and multiple systems in stellar
soft X-ray surveys and the contamination by more evolved systems, like RS
CVn's. We classified stars on the basis of Li abundance and give a glimpse of
their sky distribution. The sample appears to be a mixture of young
Pleiades-/Hyades- like stars plus an older Li-poor population (~1-2 Gyr). 7
stars with Li abundance compatible with the age of IC 2602 (~30 Myr) or younger
were detected as well, although 2 appear to be Li-rich giants. The discovery of
a large number of Li-rich giants is another outcome of this survey. The
contamination of soft X-ray surveys by old systems in which the activity level
is enhanced by tidal synchronisation is not negligible, especially for K-type
stars. 5 stars with Li content close to the primordial abundance are probably
associated with known moving groups in the solar neighbourhood. Some of them
are PTTS candidates according to their positions in the HR diagram.Comment: 16 pages, 12 figures, 6 tables; 2 figures and 2 tables in electronic
form only. Paper accepted by Astronomy and Astrophysic
Is project-based learning effective among kindergarten and elementary students? A systematic review
Project-based learning (PjBL) is becoming widespread in many schools. However, the evidence of its effectiveness in the classroom is still limited, especially in basic education. The aim of the present study was to perform a systematic review of the empirical evidence assessing the impact of PjBL on academic achievement of kindergarten and elementary students. We also examined the quality of studies, their compliance with basic prerequisites for a successful result, and their fidelity towards the key elements of PBL intervention. For this objective, we conducted a literature search in January 2020. The inclusion criteria for the review required that studies followed a pre-post design with control group and measured quantitatively the impact of PBL on content knowledge of students. The final sample included eleven articles comprising data from 722 students. The studies yielded inconclusive results, had important methodological flaws, and reported insufficient or no information about important aspects of the materials, procedure and key requirements from students and instructors to guarantee the success of PjBL. Educational implications of these results are discussed
Universal transport signatures in two-electron molecular quantum dots: gate-tunable Hund's rule, underscreened Kondo effect and quantum phase transitions
We review here some universal aspects of the physics of two-electron
molecular transistors in the absence of strong spin-orbit effects. Several
recent quantum dots experiments have shown that an electrostatic backgate could
be used to control the energy dispersion of magnetic levels. We discuss how the
generically asymmetric coupling of the metallic contacts to two different
molecular orbitals can indeed lead to a gate-tunable Hund's rule in the
presence of singlet and triplet states in the quantum dot. For gate voltages
such that the singlet constitutes the (non-magnetic) ground state, one
generally observes a suppression of low voltage transport, which can yet be
restored in the form of enhanced cotunneling features at finite bias. More
interestingly, when the gate voltage is controlled to obtain the triplet
configuration, spin S=1 Kondo anomalies appear at zero-bias, with non-Fermi
liquid features related to the underscreening of a spin larger than 1/2.
Finally, the small bare singlet-triplet splitting in our device allows to
fine-tune with the gate between these two magnetic configurations, leading to
an unscreening quantum phase transition. This transition occurs between the
non-magnetic singlet phase, where a two-stage Kondo effect occurs, and the
triplet phase, where the partially compensated (underscreened) moment is akin
to a magnetically "ordered" state. These observations are put theoretically
into a consistent global picture by using new Numerical Renormalization Group
simulations, taylored to capture sharp finie-voltage cotunneling features
within the Coulomb diamonds, together with complementary out-of-equilibrium
diagrammatic calculations on the two-orbital Anderson model. This work should
shed further light on the complicated puzzle still raised by multi-orbital
extensions of the classic Kondo problem.Comment: Review article. 16 pages, 17 figures. Minor corrections and extra
references added in V
PEAKTRAMS: An automated computational approach for the simultaneous detection of features in reverse phase and hilic hrms screening
Comparison of chromatograms obtained in reserved phase (RP) liquid chromatography and hydrophilic interaction liquid chromatography (HILIC) can provide valuable information for the identification and confirmation of suspect and non-target compounds. The plausibility of the obtained chromatographic retention times (RTs) in both modes as well as the ψomparison of the MS/MS spectra are strong points to be considered. This work presents the development of a novel automatic approach for the identification of common peaks between RP and HILIC chromatograms. The core of the program is written in R-project while a simple and user friendly graphical user interface (GUI) was built in JAVA.
The first step consists of the introduction of the target chromatograms of the same sample (one obtained by RP and one by HILIC) plus the corresponding blank chromatograms. Blank
subtraction was performed first using an algorithm to find in each scan the common m/z features (with a given mass accuracy). This algorithm also considers the RTs (a tolerance interval is applied), so the subtraction takes place even with slight drifts in the RTs between target and blank chromatograms. After blank subtraction, two different lists are obtained with the detected peaks in both RP and HILIC modes. Subsequently, m/z values are compared and matches are listed.
The developed workflow was validated with solvent standards and with spiked wastewater samples with a mixture of compounds with a wide range of physicochemical properties.
Successful results were obtained for 26 out of the 27 evaluated substances, allowing the recording of the corresponding RTs in both RP and HILIC mode
Orthogonal Polynomial Representation of Imaginary-Time Green's Functions
We study the expansion of single-particle and two-particle imaginary-time
Matsubara Green's functions of quantum impurity models in the basis of Legendre
orthogonal polynomials. We discuss various applications within the dynamical
mean-field theory (DMFT) framework. The method provides a more compact
representation of the Green's functions than standard Matsubara frequencies and
therefore significantly reduces the memory-storage size of these quantities.
Moreover, it can be used as an efficient noise filter for various physical
quantities within the continuous-time quantum Monte Carlo impurity solvers
recently developed for DMFT and its extensions. In particular, we show how to
use it for the computation of energies in the context of realistic DMFT
calculations in combination with the local density approximation to the density
functional theory (LDA+DMFT) and for the calculation of lattice
susceptibilities from the local irreducible vertex function.Comment: 14 pages, 11 figure
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