1,066 research outputs found
Ikaros represses and activates PU.1 cell-type-specifically through the multifunctional Sfpi1 URE and a myeloid specific enhancer
Generation of myeloid and lymphoid cells from progenitors involves dynamic changes in transcription factor expression and use, and disruption of hematopoietic transcription factor function and expression can contribute to leukemic transformation. PU.1 and Ikaros are pivotal factors whose expression and utilization are dynamically altered during hematopoietic development. Here, we demonstrate that expression of PU.1, encoded by the Sfpi1 gene, is divergently regulated by Ikaros in distinct cell type-specific contexts. Chromatin immune precipitation analysis and functional perturbations revealed that Ikaros can directly repress or activate Sfpi1 transcription via different PU.1 cis-elements, with PU.1 and Ikaros collaborating at myeloid-specific elements but not at other elements. Our results thus shed light on how PU.1 and Ikaros can act as lineage competency factors to facilitate both myeloid and lymphoid developmental programs
A dynamic assembly of diverse transcription factors integrates activation and cell-type information for interleukin 2 gene regulation.
Left extralobar pulmonary sequestration and a right aorto-topulmonary vein fistula in a newborn : a 3-mm thoracoscopic monolateral approach
An extralobar pulmonary sequestration (EPS) associated with a contralateral aorto-to-pulmonary vein fistula is rare. We report the case of a female newborn with left EPS fed by an artery originating from the distal thoracic aorta and, symmetrically on the controlateral side, an artery shunting in the inferior right pulmonary vein. Echocardiography showed dilatation of the left atrium. On the 34th day since birth (weight 4500 g), the patient was operated on thoracoscopically. The EPS was closed with a 3-mm sealing system, divided and removed. A window in the mediastinal pleura was created, and the origin of the fistula was identified and sealed. The postoperative course was uneventful. The patient was discharged on Day 4 with no echocardiographic signs of persistence of the fistula and of the congestive heart failure. This is the first case report of a thoracic large systemic circulation-to-pulmonary vein fistula causing heart failure associated with EPS. The thoracoscopic monolateral approach and the availability of 3-mm instruments guaranteed a maximum level of minimal invasiveness
Launching the T-cell-lineage developmental programme
Multipotent blood progenitor cells enter the thymus and begin a protracted differentiation process in which they gradually acquire T-cell characteristics while shedding their legacy of developmental plasticity. Notch signalling and basic helix-loop-helix E-protein transcription factors collaborate repeatedly to trigger and sustain this process throughout the period leading up to T-cell lineage commitment. Nevertheless, the process is discontinuous with separately regulated steps that demand roles for additional collaborating factors. This Review discusses new evidence on the coordination of specification and commitment in the early T-cell pathway; effects of microenvironmental signals; the inheritance of stem-cell regulatory factors; and the ensemble of transcription factors that modulate the effects of Notch and E proteins, to distinguish individual stages and to polarize T-cell-lineage fate determination
Interleukin 2 transcription factors as molecular targets of cAMP inhibition: delayed inhibition kinetics and combinatorial transcription roles.
Dynamic Nonlinear X-waves for Femtosecond Pulse Propagation in Water
Recent experiments on femtosecond pulses in water displayed long distance
propagation analogous to that reported in air. We verify this phenomena
numerically and show that the propagation is dynamic as opposed to self-guided.
Furthermore, we demonstrate that the propagation can be interpreted as due to
dynamic nonlinear X-waves whose robustness and role in long distance
propagation is shown to follow from the interplay between nonlinearity and
chromatic dispersion.Comment: 4 page
Measurement of scaling laws for shock waves in thermal nonlocal media
We are able to detect the details of spatial optical collisionless
wave-breaking through the high aperture imaging of a beam suffering shock in a
fluorescent nonlinear nonlocal thermal medium. This allows us to directly
measure how nonlocality and nonlinearity affect the point of shock formation
and compare results with numerical simulations.Comment: 4 pages, 4 figure
On the Properties of Two Pulses Propagating Simultaneously in Different Dispersion Regimes in a Nonlinear Planar Waveguide
Properties of two pulses propagating simultaneously in different dispersion
regimes, anomalous and normal, in a Kerr-type planar waveguide are studied in
the framework of the nonlinear Schroedinger equation. Catastrophic
self-focusing and spatio-temporal splitting of the pulses is investigated. For
the limiting case when the dispersive term of the pulse propagating in the
normal dispersion regime can be neglected an indication of a possibility of a
stable self-trapped propagation of both pulses is obtained.Comment: 18 pages (including 15 eps figures
Multiple scattering of photons by atomic hyperfine multiplets
Mesoscopic interference effects in multiple scattering of photons depend
crucially on the internal structure of the scatterers. In the present article,
we develop the analytical theory of multiple photon scattering by cold atoms
with arbitrary internal hyperfine multiplets. For a specific application, we
calculate the enhancement factor of elastic coherent backscattering as a
function of detuning from an entire hyperfine multiplet of neighboring
resonances that cannot be considered isolated. Our theory permits to understand
why atoms behave differently from classical Rayleigh point-dipole scatterers,
and how the classical description is recovered for larger but still microscopic
objects like molecules or clusters.Comment: minor changes, published versio
Ultra-short pulses in linear and nonlinear media
We consider the evolution of ultra-short optical pulses in linear and
nonlinear media. For the linear case, we first show that the initial-boundary
value problem for Maxwell's equations in which a pulse is injected into a
quiescent medium at the left endpoint can be approximated by a linear wave
equation which can then be further reduced to the linear short-pulse equation.
A rigorous proof is given that the solution of the short pulse equation stays
close to the solutions of the original wave equation over the time scales
expected from the multiple scales derivation of the short pulse equation. For
the nonlinear case we compare the predictions of the traditional nonlinear
Schr\"odinger equation (NLSE) approximation which those of the short pulse
equation (SPE). We show that both equations can be derived from Maxwell's
equations using the renormalization group method, thus bringing out the
contrasting scales. The numerical comparison of both equations to Maxwell's
equations shows clearly that as the pulse length shortens, the NLSE
approximation becomes steadily less accurate while the short pulse equation
provides a better and better approximation
- …