1,876 research outputs found
Repression of glucocorticoid-stimulated angiopoietin-like 4 gene transcription by insulin.
Angiopoietin-like 4 (Angptl4) is a glucocorticoid receptor (GR) primary target gene in hepatocytes and adipocytes. It encodes a secreted protein that inhibits extracellular LPL and promotes adipocyte lipolysis. In Angptl4 null mice, glucocorticoid-induced adipocyte lipolysis and hepatic steatosis are compromised. Markedly, insulin suppressed glucocorticoid-induced Angptl4 transcription. To unravel the mechanism, we utilized small molecules to inhibit insulin signaling components and found that phosphatidylinositol 3-kinase and Akt were vital for the suppression in H4IIE cells. A forkhead box transcription factor response element (FRE) was found near the 15 bp Angptl4 glucocorticoid response element (GRE). Mutating the Angptl4 FRE significantly reduced glucocorticoid-induced reporter gene expression in cells. Moreover, chromatin immunoprecipitation revealed that GR and FoxO1 were recruited to Angptl4 GRE and FRE in a glucocorticoid-dependent manner, and cotreatment with insulin abolished both recruitments. Furthermore, in 24 h fasted mice, significant occupancy of GR and FoxO1 at the Angptl4 GRE and FRE was found in the liver. In contrast, both occupancies were diminished after 24 h refeeding. Finally, overexpression of dominant negative FoxO1 mutant abolished glucocorticoid-induced Angptl4 expression, mimicking the insulin suppression. Overall, we demonstrate that both GR and FoxO1 are required for Angptl4 transcription activation, and that FoxO1 negatively mediates the suppressive effect of insulin
The use of classifiers in typically developing and language-delayed preschoolers
Thesis (B.Sc)--University of Hong Kong, 2008.Includes bibliographical references (leaves 29-30).Also available in print.A dissertation submitted in partial fulfilment of the requirements for the Bachelor of Science (Speech and Hearing Sciences), The University of Hong Kong, June 30, 2008.published_or_final_versionSpeech and Hearing SciencesBachelorBachelor of Science in Speech and Hearing Science
Evidence for (and Against) Progenitor Bias in the Size Growth of Compact Red Galaxies
Most massive passive galaxies are compact at high redshifts, but similarly
compact massive galaxies are rare in the local universe. The most common
interpretation of this phenomenon is that massive galaxies have grown in size
by a factor of about five since redshift z=2. An alternative explanation is
that recently quenched massive galaxies are larger (a "progenitor bias"). In
this paper we explore the importance of progenitor bias by looking for
systematic differences in the stellar populations of compact early-type
galaxies in the DEEP2 survey as a function of size. Our analysis is based on
applying the statistical technique of bootstrap resampling to constrain
differences in the median ages of our samples and to begin to characterize the
distribution of stellar populations in our co-added spectra. The light-weighted
ages of compact early-type galaxies at redshifts 0.5 < z < 1.4 are compared to
those of a control sample of larger galaxies at similar redshifts. We find that
massive compact early-type galaxies selected on the basis of red color and high
bulge-to-total ratio are younger than similarly selected larger galaxies,
suggesting that size growth in these objects is not driven mainly by progenitor
bias, and that individual galaxies grow as their stellar populations age.
However, compact early-type galaxies selected on the basis of image smoothness
and high bulge-to-total ratio are older than a control sample of larger
galaxies. Progenitor bias will play a significant role in defining the apparent
size changes of early-type galaxies if they are selected on the basis of the
smoothness of their light distributions.Comment: 39 pages, 10 figures. Astrophysical Journal (in press
Spatial and temporal colonization dynamics of segmented filamentous bacteria is influenced by gender, age and experimental infection with Helicobacter hepaticus in Swiss Webster mice
In this study, we examined colonization dynamics of segmented filamentous bacteria (SFB) in intestine of Swiss Webster (SW) mice infected with Helicobacter hepaticus (Hh). At 8 weeks post-inoculation with Hh (WPI), cecal and colonic SFB levels in the control males were significantly lower compared to those at 16 WPI. Hh infection in both genders did not alter SFB levels in the jejunum and ileum, but increased SFB levels in the cecum and colon of males compared to the controls (P < 0.05) at 8 WPI. At 16 WPI, the Hh-infected females contained lower levels of SFB in the jejunum, cecum and colon compared to the female controls. Irrespective of gender, aging and Hh infection, the Il-17A mRNA levels decreased from the small intestine to the cecum and then to the colon, whereas the Foxp3 mRNA levels were comparable in these intestinal regions. There were significant differences in Il-17A mRNA levels in the ileum (P < 0.05, R2 = 0.31), with females having greater Il-17A mRNA levels than males, and higher SFB colonization levels related to more Il-17A mRNA. These results indicate that aging and gender play an important role in colonization dynamics of intestinal SFB and ileal SFB-associated Th17 response.United States. National Institutes of Health (P30-ES002109)United States. National Institutes of Health (R01OD11141)United States. National Institutes of Health (R01-CA067529
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Film Director: Cheung Tammy (張虹)
Film Release Year: 2003https://commons.ln.edu.hk/ccs_worksheet/1003/thumbnail.jp
Testing Diagnostics of Nuclear Activity and Star Formation in Galaxies at z>1
We present some of the first science data with the new Keck/MOSFIRE
instrument to test the effectiveness of different AGN/SF diagnostics at z~1.5.
MOSFIRE spectra were obtained in three H-band multi-slit masks in the GOODS-S
field, resulting in two hour exposures of 36 emission-line galaxies. We compare
X-ray data with the traditional emission-line ratio diagnostics and the
alternative mass-excitation and color-excitation diagrams, combining new
MOSFIRE infrared data with previous HST/WFC3 infrared spectra (from the 3D-HST
survey) and multiwavelength photometry. We demonstrate that a high [OIII]/Hb
ratio is insufficient as an AGN indicator at z>1. For the four X-ray detected
galaxies, the classic diagnostics ([OIII]/Hb vs. [NII]/Ha and [SII]/Ha) remain
consistent with X-ray AGN/SF classification. The X-ray data also suggest that
"composite" galaxies (with intermediate AGN/SF classification) host bona-fide
AGNs. Nearly 2/3 of the z~1.5 emission-line galaxies have nuclear activity
detected by either X-rays or the classic diagnostics. Compared to the X-ray and
line ratio classifications, the mass-excitation method remains effective at
z>1, but we show that the color-excitation method requires a new calibration to
successfully identify AGNs at these redshifts.Comment: 7 pages, 4 figures. Accepted to ApJ Letter
Tunable waveguide and cavity in a phononic crystal plate by controlling whispering-gallery modes in hollow pillars
International audienceWe investigate the properties of a phononic crystal plate with hollow pillars and introduce the existence of whispering-gallery modes (WGMs). We show that by tuning the inner radius of the hollow pillar, these modes can merge inside both Bragg and low frequency band gaps, deserving phononic crystal and acoustic metamaterial applications. These modes can be used as narrow pass bands for which the quality factor can be greatly enhanced by the introduction of an additional cylinder between the hollow cylinder and the plate. We discuss some functionalities of these confined WGM in both Bragg and low frequency gaps for wavelength division in multiplexer devices using heteroradii pillars introduced into waveguide and cavity structures
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