45 research outputs found
Molecular line survey of Sagittarius B2(M) from 330 to 355 GHz and comparison with Sagittarius B2(N)
We have surveyed molecular line emission from Sgr B2 over the range from 330 to 355 GHz at the position designated Sgr B2(M). This position is prominent in millimeter continuum maps of the region and is associated with a compact H II region, a hot NH_3 core, and sources of H_2O and OH maser emission. We have also obtained observations contrasting the submillimeter molecular emission from Sgr B2(M) and Sgr B2(N), an additional center of activity thought to be a dense protostellar core.
The picture of the interstellar chemistry of these regions which we derive is substantially different from that
determined from previous observations at lower frequencies and with lower spatial resolution. In particular,
molecules such as SO_2 and CH_3OH dominate the submillimeter spectrum to a much greater extent than they do
the low-frequency observations. Much of this difference is due to the higher spatial resolution of the submillimeter
observations, which makes them much more sensitive to emission from compact, dense cores. The millimeter
data were most effective at sampling material in the surrounding lower density regions. The chemistry of the core
sources in Sgr B2 appears similar to that of other dense cores, such as the core of the Orion molecular cloud.
The spectral differences between Sgr B2(M) and Sgr B2(N) primarily relate to differences in excitation and
column density. For most molecular species the northern source (N) has a column density significantly higher
than that found in the middle source (M), often by a factor of about 5. The principal exceptions are the species SO
and SO_2 which seem to be substantially more abundant in the middle source. Generally excitation seems to be
higher in the northern source, suggesting a somewhat higher density core, although there are some departures
indicating that the excitation situation is more complicated. High optical depths in many of the submillimeter transitions systematically bias the interpretation of both column densities and excitation. Many of the millimeter lines may also have high optical depths, particularly those lines arising from the compact core sources
Expression patterns and functional evaluation of the UNC5b receptor during the early phase of peripheral nerve regeneration using the mouse median nerve model.
Application of 2 different hemostatic procedures during microsurgical median nerve reconstruction in the rat does not hinder axonal regeneration.
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Foxc1 is required by pericytes during fetal brain angiogenesis
Summary Brain pericytes play a critical role in blood vessel stability and blood–brain barrier maturation. Despite this, how brain pericytes function in these different capacities is only beginning to be understood. Here we show that the forkhead transcription factor Foxc1 is expressed by brain pericytes during development and is critical for pericyte regulation of vascular development in the fetal brain. Conditional deletion of Foxc1 from pericytes and vascular smooth muscle cells leads to late-gestation cerebral micro-hemorrhages as well as pericyte and endothelial cell hyperplasia due to increased proliferation of both cell types. Conditional Foxc1 mutants do not have widespread defects in BBB maturation, though focal breakdown of BBB integrity is observed in large, dysplastic vessels. qPCR profiling of brain microvessels isolated from conditional mutants showed alterations in pericyte-expressed proteoglycans while other genes previously implicated in pericyte–endothelial cell interactions were unchanged. Collectively these data point towards an important role for Foxc1 in certain brain pericyte functions (e.g. vessel morphogenesis) but not others (e.g. barriergenesis)