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Identification of methotrexate as a heterochromatin-promoting drug.
Heterochromatin is a tightly packed form of DNA involved in gene silencing, chromosome segregation, and protection of genome stability. Heterochromatin is becoming more recognized in tumor suppression and may thus serve as a potential target for cancer therapy. However, to date there are no drugs that are well established to specifically promote heterochromatin formation. Here, we describe a screening method using Drosophila to identify small molecule compounds that promote heterochromatin formation, with the purpose of developing epigenetic cancer therapeutics. We took advantage of a Drosophila strain with a variegated eye color phenotype that is sensitive to heterochromatin levels, and screened a library of 97 FDA approved oncology drugs. This screen identified methotrexate as the most potent small molecule drug, among the 97 oncology drugs screened, in promoting heterochromatin formation. Interestingly, methotrexate has been identified as a JAK/STAT inhibitor in a functional screen, causing reduced phosphorylation of STAT proteins. These findings are in line with our previous observation that unphosphorylated STAT (uSTAT) promotes heterochromatin formation in both Drosophila and human cells and suppresses tumor growth in mouse xenografts. Thus, Drosophila with variegated eye color phenotypes could be an effective tool for screening heterochromatin-promoting compounds that could be candidates as cancer therapeutics
Roles of TRPV1 and neuropeptidergic receptors in dorsal root reflex-mediated neurogenic inflammation induced by intradermal injection of capsaicin
<p>Abstract</p> <p>Background</p> <p>Acute cutaneous neurogenic inflammation initiated by activation of transient receptor potential vanilloid-1 (TRPV<sub>1</sub>) receptors following intradermal injection of capsaicin is mediated mainly by dorsal root reflexes (DRRs). Inflammatory neuropeptides are suggested to be released from primary afferent nociceptors participating in inflammation. However, no direct evidence demonstrates that the release of inflammatory substances is due to the triggering of DRRs and how activation of TRPV<sub>1 </sub>receptors initiates neurogenic inflammation via triggering DRRs.</p> <p>Results</p> <p>Here we used pharmacological manipulations to analyze the roles of TRPV<sub>1 </sub>and neuropeptidergic receptors in the DRR-mediated neurogenic inflammation induced by intradermal injection of capsaicin. The degree of cutaneous inflammation in the hindpaw that followed capsaicin injection was assessed by measurements of local blood flow (vasodilation) and paw-thickness (edema) of the foot skin in anesthetized rats. Local injection of capsaicin, calcitonin gene-related peptide (CGRP) or substance P (SP) resulted in cutaneous vasodilation and edema. Removal of DRRs by either spinal dorsal rhizotomy or intrathecal administration of the GABA<sub>A </sub>receptor antagonist, bicuculline, reduced dramatically the capsaicin-induced vasodilation and edema. In contrast, CGRP- or SP-induced inflammation was not significantly affected after DRR removal. Dose-response analysis of the antagonistic effect of the TRPV<sub>1 </sub>receptor antagonist, capsazepine administered peripherally, shows that the capsaicin-evoked inflammation was inhibited in a dose-dependent manner, and nearly completely abolished by capsazepine at doses between 30–150 μg. In contrast, pretreatment of the periphery with different doses of CGRP<sub>8–37 </sub>(a CGRP receptor antagonist) or spantide I (a neurokinin 1 receptor antagonist) only reduced the inflammation. If both CGRP and NK<sub>1 </sub>receptors were blocked by co-administration of CGRP<sub>8–37 </sub>and spantide I, a stronger reduction in the capsaicin-initiated inflammation was produced.</p> <p>Conclusion</p> <p>Our data suggest that 1) the generation of DRRs is critical for driving the release of neuropeptides antidromically from primary afferent nociceptors; 2) activation of TRPV<sub>1 </sub>receptors in primary afferent nociceptors following intradermal capsaicin injection initiates this process; 3) the released CGRP and SP participate in neurogenic inflammation.</p
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Diurnal seismicity cycle linked to subsurface melting on an ice shelf
ABSTRACTSeismograms acquired on the McMurdo Ice Shelf, Antarctica, during an Austral summer melt season (November 2016–January 2017) reveal a diurnal cycle of seismicity, consisting of hundreds of thousands of small ice quakes limited to a 6–12 hour period during the evening, in an area where there is substantial subsurface melting. This cycle is explained by thermally induced bending and fracture of a frozen surface superimposed on a subsurface slush/water layer that is supported by solar radiation penetration and absorption. A simple, one-dimensional model of heat transfer driven by observed surface air temperature and shortwave absorption reproduces the presence and absence (as daily weather dictated) of the observed diurnal seismicity cycle. Seismic event statistics comparing event occurrence with amplitude suggest that the events are generated in a fractured medium featuring relatively low stresses, as is consistent with a frozen surface superimposed on subsurface slush. Waveforms of the icequakes are consistent with hydroacoustic phases at frequency and flexural-gravity waves at frequency . Our results suggest that seismic observation may prove useful in monitoring subsurface melting in a manner that complements other ground-based methods as well as remote sensing.</jats:p
Spectral method for matching exterior and interior elliptic problems
A spectral method is described for solving coupled elliptic problems on an
interior and an exterior domain. The method is formulated and tested on the
two-dimensional interior Poisson and exterior Laplace problems, whose solutions
and their normal derivatives are required to be continuous across the
interface. A complete basis of homogeneous solutions for the interior and
exterior regions, corresponding to all possible Dirichlet boundary values at
the interface, are calculated in a preprocessing step. This basis is used to
construct the influence matrix which serves to transform the coupled boundary
conditions into conditions on the interior problem. Chebyshev approximations
are used to represent both the interior solutions and the boundary values. A
standard Chebyshev spectral method is used to calculate the interior solutions.
The exterior harmonic solutions are calculated as the convolution of the
free-space Green's function with a surface density; this surface density is
itself the solution to an integral equation which has an analytic solution when
the boundary values are given as a Chebyshev expansion. Properties of Chebyshev
approximations insure that the basis of exterior harmonic functions represents
the external near-boundary solutions uniformly. The method is tested by
calculating the electrostatic potential resulting from charge distributions in
a rectangle. The resulting influence matrix is well-conditioned and solutions
converge exponentially as the resolution is increased. The generalization of
this approach to three-dimensional problems is discussed, in particular the
magnetohydrodynamic equations in a finite cylindrical domain surrounded by a
vacuum
2009-2010 Mostly Music: Haydn
https://spiral.lynn.edu/conservatory_mostlymusic/1006/thumbnail.jp
An hydrodynamic shear instability in stratified disks
We discuss the possibility that astrophysical accretion disks are dynamically
unstable to non-axisymmetric disturbances with characteristic scales much
smaller than the vertical scale height. The instability is studied using three
methods: one based on the energy integral, which allows the determination of a
sufficient condition of stability, one using a WKB approach, which allows the
determination of the necessary and sufficient condition for instability and a
last one by numerical solution. This linear instability occurs in any inviscid
stably stratified differential rotating fluid for rigid, stress-free or
periodic boundary conditions, provided the angular velocity decreases
outwards with radius . At not too small stratification, its growth rate is a
fraction of . The influence of viscous dissipation and thermal
diffusivity on the instability is studied numerically, with emphasis on the
case when (Keplerian case). Strong
stratification and large diffusivity are found to have a stabilizing effect.
The corresponding critical stratification and Reynolds number for the onset of
the instability in a typical disk are derived. We propose that the spontaneous
generation of these linear modes is the source of turbulence in disks,
especially in weakly ionized disks.Comment: 19 pages, 13 figures, to appear in A&
K2: A new method for the detection of galaxy clusters based on CFHTLS multicolor images
We have developed a new method, K2, optimized for the detection of galaxy
clusters in multicolor images. Based on the Red Sequence approach, K2 detects
clusters using simultaneous enhancements in both colors and position. The
detection significance is robustly determined through extensive Monte-Carlo
simulations and through comparison with available cluster catalogs based on two
different optical methods, and also on X-ray data. K2 also provides
quantitative estimates of the candidate clusters' richness and photometric
redshifts. Initially K2 was applied to 161 sq deg of two color gri images of
the CFHTLS-Wide data. Our simulations show that the false detection rate, at
our selected threshold, is only ~1%, and that the cluster catalogs are ~80%
complete up to a redshift of 0.6 for Fornax-like and richer clusters and to z
~0.3 for poorer clusters. Based on Terapix T05 release gri photometric
catalogs, 35 clusters/sq deg are detected, with 1-2 Fornax-like or richer
clusters every two square degrees. Catalogs containing data for 6144 galaxy
clusters have been prepared, of which 239 are rich clusters. These clusters,
especially the latter, are being searched for gravitational lenses -- one of
our chief motivations for cluster detection in CFHTLS. The K2 method can be
easily extended to use additional color information and thus improve overall
cluster detection to higher redshifts. The complete set of K2 cluster catalogs,
along with the supplementary catalogs for the member galaxies, are available on
request from the authors.Comment: Accepted in ApJ. 25 pages, including 10 figures. Latex with
emulateapj v03/07/0
Fermion Pairing Dynamics in the Relativistic Scalar Plasma
Using many-body techniques we obtain the time-dependent Gaussian
approximation for interacting fermion-scalar field models. This method is
applied to an uniform system of relativistic spin-1/2 fermion field coupled,
through a Yukawa term, to a scalar field in 3+1 dimensions, the so-called
quantum scalar plasma model. The renormalization for the resulting Gaussian
mean-field equations, both static and dynamical, are examined and initial
conditions discussed. We also investigate solutions for the gap equation and
show that the energy density has a single minimum.Comment: 21 pages, latex, 4 postscript figures, new sections, some literary
changes, notation corrections, accepted for publication in Phys. Rev
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