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Quantification of Dehydroepiandrosterone, 17Ī²-Estradiol, Testosterone, and Their Sulfates in Mouse Tissues by LC-MS/MS.
We report a high-performance, liquid chromatography/tandem mass spectrometry (HPLC-MS/MS) assay to quantify without derivatizaton dehyroepiandrosterone (DHEA), 17Ī²-estradiol (E2), testosterone (T), and their sulfates in serum and tissues. This assay functions well with multiple adipose depots, a previously unattained analysis. To delipidate and facilitate recovery, tissues were homogenized in acetonitrile, and the homogenate was frozen. The supernatant was evaporated, resuspended in an aqueous acetate buffer, and extracted with hexane to separate free (unconjugated) from sulfated steroids. Sulfated steroids in the aqueous medium were then hydrolyzed with sulfatase and extracted with hexane. Each extract was analyzed separately. HPLC resolution combined with the sensitivity and specificity of MS/MS allowed quantification of DHEA, E2, and T with 10, 10, and 5 fmol lower limits of quantification and linear ranges to 1 pmol. Application of the method to mouse serum and tissues reveals ranges of DHEA, E2, and T and their sulfates, and tissue-specific differences in steroid profile, especially white versus brown adipose. In addition, marginal decreases of T in all tissues and considerable increases in DHEA in male iWAT and eWAT in response to a high-fat diet further strengthen the inference regarding the role of steroid metabolism in adipogenesis. This assay permits detailed studies of interactions between adiposity and sex steroids in serum and tissues, including adipose
Viscoelastic Behavior of Solid He
Over the last five years several experimental groups have reported anomalies
in the temperature dependence of the period and amplitude of a torsional
oscillator containing solid He. We model these experiments by assuming that
He is a viscoelastic solid--a solid with frequency dependent internal
friction. We find that while our model can provide a quantitative account of
the dissipation observed in the torsional oscillator experiments, it only
accounts for about 10% of the observed period shift, leaving open the
possibility that the remaining period shift is due to the onset of
superfluidity in the sample.Comment: 4 pages, 3 figure
Correlation between fracture surface morphology and toughness in Zr-based bulk metallic glasses
Fracture surfaces of Zr-based bulk metallic glasses of various compositions tested in the as-cast and annealed conditions were analyzed using scanning electron microscopy. The tougher samples have shown highly jagged patterns at the beginning stage of crack propagation, and the length and roughness of this jagged pattern correlate well with the measured fracture toughness values. These jagged patterns, the main source of energy dissipation in the sample, are attributed to the formation of shear bands inside the sample. This observation provides strong evidence of significant āplastic zoneā screening at the crack tip
In-situ electrochemical fabrication of natural contacts on single nanowires
We report a template-based in-situ electrochemical method for fabricating
natural electric contacts on single nanowires using a pair of cross-patterned
electrodes. Such electric contacts are highly stable upon thermal cycling
between room temperature and milli-Kelvin temperatures. Direct imaging of the
single-nanowire contacts using scanning electron microscopy is also
demonstrated.Comment: 13 pages, 4 figure
Language Games in Computer-Mediated Communication
Drawn upon WittgensteinĆ¢ā¬ā¢s theory of language games, we propose a pragmatic perspective of organizational communication, which unites research in media richness, sense-making, and conversation analysis. We conducted a comparative study of face-to-face versus computer-mediated reference transactions in an academic library and found that communicative context impacts the way people use language, and people consciously utilize linguistic signals to create a communicative context, especially a context of politeness
A Statistical Characterization of Shadowed Fading in Indoor Off-Body Communications Channels At 5.8 GHz
Reaper is regulated by IAP-mediated ubiquitination
In most cases, apoptotic cell death culminates in the activation of the caspase family of cysteine proteases, leading to the orderly dismantling and elimination of the cell. The IAPs (inhibitors of apoptosis) comprise a family of proteins that oppose caspases and thus act to raise the apoptotic threshold. Disruption of IAP-mediated caspase inhibition has been shown to be an important activity for pro-apoptotic proteins in Drosophila (Reaper, HID, and Grim) and in mammalian cells (Smac/DIABLO and Omi/HtrA2). In addition, in the case of the fly, these proteins are able to stimulate the ubiquitination and degradation of IAPs by a mechanism involving the ubiquitin ligase activity of the IAP itself. In this report, we show that the Drosophila RHG proteins (Reaper, HID, and Grim) are themselves substrates for IAP-mediated ubiquitination. This ubiquitination of Reaper requires IAP ubiquitin-ligase activity and a stable interaction between Reaper and the IAP. Additionally, degradation of Reaper can be blocked by mutating its potential ubiquitination sites. Most importantly, we also show that regulation of Reaper by ubiquitination is a significant factor in determining its biological activity. These data demonstrate a novel function for IAPs and suggest that IAPs and Reaper-like proteins mutually control each other's abundance
The Drosophila Caspase DRONC Cleaves following Glutamate or Aspartate and Is Regulated by DIAP1, HID, and GRIM
The caspase family of cysteine proteases plays important roles in bringing about apoptotic cell death. All caspases studied to date cleave substrates COOH-terminal to an aspartate. Here we show that the Drosophila caspase DRONC cleaves COOH-terminal to glutamate as well as aspartate. DRONC autoprocesses itself following a glutamate residue, but processes a second caspase, drICE, following an aspartate. DRONC prefers tetrapeptide substrates in which aliphatic amino acids are present at the P2 position, and the P1 residue can be either aspartate or glutamate. Expression of a dominant negative form of DRONC blocks cell death induced by the Drosophila cell death activators reaper, hid, and grim, and DRONC overexpression in flies promotes cell death. Furthermore, the Drosophila cell death inhibitor DIAP1 inhibits DRONC activity in yeast, and DIAP1's ability to inhibit DRONC-dependent yeast cell death is suppressed by HID and GRIM. These observations suggest that DRONC acts to promote cell death. However, DRONC activity is not suppressed by the caspase inhibitor and cell death suppressor baculovirus p35. We discuss possible models for DRONC function as a cell death inhibitor
Discovery and Optimization of Inhibitors of DNA Methyltransferase as Novel Drugs for Cancer Therapy
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