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Mef2 induction of the immediate early gene Hr38/Nr4a is terminated by Sirt1 to promote ethanol tolerance.
Drug naïve animals given a single dose of ethanol show changed responses to subsequent doses, including the development of ethanol tolerance and ethanol preference. These simple forms of behavioral plasticity are due in part to changes in gene expression and neuronal properties. Surprisingly little is known about how ethanol initiates changes in gene expression or what the changes do. Here we demonstrate a role in ethanol plasticity for Hr38, the sole Drosophila homolog of the mammalian Nr4a1/2/3 class of immediate early response transcription factors. Acute ethanol exposure induces transient expression of Hr38 and other immediate early neuronal activity genes. Ethanol activates the Mef2 transcriptional activator to induce Hr38, and the Sirt1 histone/protein deacetylase is required to terminate Hr38 induction. Loss of Hr38 decreases ethanol tolerance and causes precocious but short-lasting ethanol preference. Similarly, reduced Mef2 activity in all neurons or specifically in the mushroom body α/β neurons decreases ethanol tolerance; Sirt1 promotes ethanol tolerance in these same neurons. Genetically decreasing Hr38 expression levels in Sirt1 null mutants restores ethanol tolerance, demonstrating that both induction and termination of Hr38 expression are important for behavioral plasticity to proceed. These data demonstrate that Hr38 functions as an immediate early transcription factor that promotes ethanol behavioral plasticity
Analysis of Quiet-Sun Internetwork Magnetic Fields Based on Linear Polarization Signals
We present results from the analysis of Fe I 630 nm measurements of the quiet
Sun taken with the spectropolarimeter of the Hinode satellite. Two data sets
with noise levels of 1.2{\times}10-3 and 3{\times}10-4 are employed. We
determine the distribution of field strengths and inclinations by inverting the
two observations with a Milne-Eddington model atmosphere. The inversions show a
predominance of weak, highly inclined fields. By means of several tests we
conclude that these properties cannot be attributed to photon noise effects. To
obtain the most accurate results, we focus on the 27.4% of the pixels in the
second data set that have linear polarization amplitudes larger than 4.5 times
the noise level. The vector magnetic field derived for these pixels is very
precise because both circular and linear polarization signals are used
simultaneously. The inferred field strength, inclination, and filling factor
distributions agree with previous results, supporting the idea that
internetwork fields are weak and very inclined, at least in about one quarter
of the area occupied by the internetwork. These properties differ from those of
network fields. The average magnetic flux density and the mean field strength
derived from the 27.4% of the field of view with clear linear polarization
signals are 16.3 Mx cm-2 and 220 G, respectively. The ratio between the average
horizontal and vertical components of the field is approximately 3.1. The
internetwork fields do not follow an isotropic distribution of orientations.Comment: To appear in APJ, Vol 749, 201
Power spectra of velocities and magnetic fields on the solar surface and their dependence on the unsigned magnetic flux density
We have performed power spectral analysis of surface temperatures,
velocities, and magnetic fields, using spectro-polarimetric data taken with the
Hinode Solar Optical Telescope. When we make power spectra in a field-of-view
covering the super-granular scale, kinetic and thermal power spectra have a
prominent peak at the granular scale while the magnetic power spectra have a
broadly distributed power over various spatial scales with weak peaks at both
the granular and supergranular scales. To study the power spectra separately in
internetwork and network regions, power spectra are derived in small
sub-regions extracted from the field-of-view. We examine slopes of the power
spectra using power-law indices, and compare them with the unsigned magnetic
flux density averaged in the sub-regions. The thermal and kinetic spectra are
steeper than the magnetic ones at the sub-granular scale in the internetwork
regions, and the power-law indices differ by about 2. The power-law indices of
the magnetic power spectra are close to or smaller than -1 at that scale, which
suggests the total magnetic energy mainly comes from either the granular scale
magnetic structures or both the granular scale and smaller ones contributing
evenly. The slopes of the thermal and kinetic power spectra become less steep
with increasing unsigned flux density in the network regions. The power-law
indices of all the thermal, kinetic, and magnetic power spectra become similar
when the unsigned flux density is larger than 200 Mx cm^-2.Comment: 9 pages, 6 figures, accepted for publication in Ap
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