404 research outputs found
Histone Deacetylase 3 (HDAC3) Regulates Lymphatic Vascular Development
Cardiovascular disease continues to be the leading cause of morbidity and mortality worldwide with an estimated 17 million annual deaths. A majority of cases are attributed to disease affecting the vascular system including arterial, venous and lymphatic vessels. Despite progress in understanding the molecular bases of vascular development and disease, the role of chromatin modifying enzymes in vascular processes remains ill defined. Here we show that the histone-modifying enzyme Hdac3 is a critical regulator of lymphatic vascular development. Endothelial specific loss of Hdac3 in mice affects the development of lymphovenous and lymphatic valves resulting in aberrant blood lymph separation, lymphedema and complete lethality. We demonstrate that Hdac3 functions in a flow responsive manner to regulate the expression of Gata2, a transcription factor essential for lymphatic valve development. In response to flow, transcription factors Tal1, Ets1/2 and Gata2 recruit Hdac3 to an evolutionarily conserved intragenic enhancer of Gata2 gene. In turn, Hdac3 recruits p300, a histone acetyl transferase, to render activation of the Gata2 enhancer, and thus promotes Gata2 transcription. Together, our findings demonstrate the molecular basis by which cell extrinsic and intrinsic cues cooperate to regulate lymphatic development
Unique Observations of a Geomagnetic SI^+ -- SI^- Pair: Solar Sources and Associated Solar Wind Fluctuations
The paper describes the occurrence of a pair of oppositely directed sudden
impulses (SI), in the geomagnetic field (X), at ground stations, called
SI -- SI pairs, that occurred between 1835 UT and 2300 UT on 23
April 1998. The SI -- SI pair, was closely correlated with
corresponding variations in the solar wind density, while solar wind velocity
and the southward component of the interplanetary magnetic field (Bz) did not
show any correspondence. Further, this event had no source on the visible solar
disk. However, a rear-side partial halo coronal mass ejection (CME) and an M1.4
class solar flare behind the west limb, took place on 20 April 1998, the date
corresponding to the traceback location of the solar wind flows. This event
presents empirical evidence, which to our knowledge, is the best convincing
evidence for the association of specific solar events to the observations of an
SI -- SI pair. In addition, it shows that it is possible for a
rear side solar flare to propagate a shock towards the earth.Comment: The paper has just been accepted in the Journal of Geophysical
Research (Space Physics) on 20 September 2010. It is 17 pages with 4 figure
A study of density modulation index in the inner heliospheric solar wind during solar cycle 23
The ratio of the rms electron density fluctuations to the background density
in the solar wind (density modulation index, )
is of vital importance in understanding several problems in heliospheric
physics related to solar wind turbulence. In this paper, we have investigated
the behavior of in the inner-heliosphere from 0.26 to 0.82 AU.
The density fluctuations have been deduced using extensive
ground-based observations of interplanetary scintillation (IPS) at 327 MHz,
which probe spatial scales of a few hundred km. The background densities ()
have been derived using near-Earth observations from the Advanced Composition
Explorer (). Our analysis reveals that and does not vary appreciably with heliocentric distance. We
also find that declines by 8% from 1998 to 2008. We discuss the
impact of these findings on problems ranging from our understanding of Forbush
decreases to the behavior of the solar wind dynamic pressure over the recent
peculiar solar minimum at the end of cycle 23..Comment: 13 Pages, 8 Figures, Accepted for publication in Ap
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