Transverse electric field–induced deformation of armchair single-walled carbon nanotube

The deformation of armchair single-walled carbon nanotube under transverse electric field has been investigated using density functional theory. The results show that the circular cross-sections of the nanotubes are deformed to elliptic ones, in which the tube diameter along the field direction is increased, whereas the diameter perpendicular to the field direction is reduced. The electronic structures of the deformed nanotubes were also studied. The ratio of the major diameter to the minor diameter of the elliptic cross-section was used to estimate the degree of the deformation. It is found that this ratio depends on the field strength and the tube diameter. However, the field direction has little role in the deformation

Winter sky brightness and cloud cover at Dome A, Antarctica

At the summit of the Antarctic plateau, Dome A offers an intriguing location for future large scale optical astronomical observatories. The Gattini Dome A project was created to measure the optical sky brightness and large area cloud cover of the winter-time sky above this high altitude Antarctic site. The wide field camera and multi-filter system was installed on the PLATO instrument module as part of the Chinese-led traverse to Dome A in January 2008. This automated wide field camera consists of an Apogee U4000 interline CCD coupled to a Nikon fisheye lens enclosed in a heated container with glass window. The system contains a filter mechanism providing a suite of standard astronomical photometric filters (Bessell B, V, R) and a long-pass red filter for the detection and monitoring of airglow emission. The system operated continuously throughout the 2009, and 2011 winter seasons and part-way through the 2010 season, recording long exposure images sequentially for each filter. We have in hand one complete winter-time dataset (2009) returned via a manned traverse. We present here the first measurements of sky brightness in the photometric V band, cloud cover statistics measured so far and an estimate of the extinction

Characterization of the regulation of renal Na+/H+ exchanger NHE3 by insulin

Insulin receptors are widely distributed in the kidney and affect multiple aspects of renal function. In the proximal tubule, insulin regulates volume and acid-base regulation through stimulation of the Na(+)/H(+) exchanger NHE3. This paper characterizes the signaling pathway by which insulin stimulates NHE3 in a cell culture model [opossum kidney (OK) cell]. Insulin has two distinct phases of action on NHE3. Chronic insulin (24 h) activates NHE3 through the classic phosphatidylinositol 3-kinase-serum- and glucocorticoid-dependent kinase 1 (PI3K-SGK1) pathway as insulin stimulates SGK1 phosphorylation and the insulin effect can be blocked by the PI3K inhibitor wortmannin or a dominant-negative SGK1. We showed that SGK1 transcript and protein are expressed in rat proximal tubule and OK cells. We previously showed that glucocorticoids augment the effect of insulin on NHE3 (Klisic J, Hu MC, Nief V, Reyes L, Fuster D, Moe OW, Ambuhl PM. Am J Physiol Renal Physiol 283: F532-F539, 2002). Part of this can be mediated via induction of SGK1 by glucocorticoids, and indeed the insulin effect on NHE3 can also be amplified by overexpression of SGK1. We next addressed the acute effect of insulin (1-2 h) on NHE3 by systematically examining the candidate signaling cascades and activation mechanisms of NHE3. We ruled out the PI3K-SGK1-Akt and TC10 pathways, increased surface NHE3, NHE3 phosphorylation, NHE3 association with calcineurin homologous protein 1 or megalin as mechanisms of acute activation of NHE3 by insulin. In summary, insulin stimulates NHE3 acutely via yet undefined pathways and mechanisms. The chronic effect of insulin is mediated by the classic PI3K-SGK1 route

Characterization of the Sodium/Hydrogen Exchanger NHA2

Cation/proton exchange has been recognized for decades in mammalian mitochondria, but the exchanger proteins have eluded identification. In this study, a cDNA from a human brain library, previously designated NHA2 in the genome, was cloned and characterized. The NHA2 transcript bears more similarity to prokaryotic than known eukaryotic sodium/proton exchangers, but it was found to be expressed in multiple mammalian organs and cultured cells. A mAb to NHA2 was generated and found to label an approximately 55-kD native protein in multiple tissues and cell lines. The specificity of this antibody was confirmed by demonstrating the loss of the native NHA2 band on immunoblots when cultured cells were treated with NHA2-specific small interfering RNA. Although NHA2 protein was detected in multiple organs, within each, its expression was restricted to specific cell types. In the kidney, co-localization with calbindin 28k and reverse transcription–PCR of microdissected tubules revealed that NHA2 is limited to the distal convoluted tubule. In cell lines, native NHA2 was localized both to the plasma membrane and to the intracellular compartment; immunogold electron microscopy of rat distal convoluted tubule demonstrated NHA2 predominantly but not exclusively on the inner mitochondrial membrane. Furthermore, co-sedimentation of NHA2 antigen and mitochondrial membranes was observed with differential centrifugation, and two mitochondrial markers co-localized with NHA2 in cultured cells. Regarding function, human NHA2 reversed the sodium/hydrogen exchanger–null phenotype when expressed in sodium/hydrogen exchanger–deficient yeast and restored the ability to defend high salinity in the presence of acidic extracellular pH. In summary, NHA2 is a ubiquitous mammalian sodium proton/exchanger that is restricted to the distal convoluted tubule in the kidney

Alpha-Klotho Enrichment in Induced Pluripotent Stem Cell Secretome Contributes to Antioxidative Protection in Acute Lung Injury.

Induced pluripotent stem cells (iPSCs) have been reported to alleviate organ injury, although the mechanisms of action remain unclear and administration of intact cells faces many limitations. We hypothesized that cell-free conditioned media (CM) containing the secretome of iPSCs possess antioxidative constituents that can alleviate pulmonary oxidant stress damage. We derived iPSCs from human dermal fibroblasts and harvested the CM. Addition of iPSC CM to cultured human alveolar type-1 epithelial cells mitigated hyperoxia-induced depletion of endogenous total antioxidant capacity while tracheal instillation of iPSC CM into adult rat lungs enhanced hyperoxia-induced increase in TAC. In both the in vitro and in vivo models, iPSC CM ameliorated oxidative damage to DNA, lipid, and protein, and activated the nuclear factor (erythroid 2)-related factor 2 (Nrf2) network of endogenous antioxidant proteins. Compared with control fibroblast-conditioned or cell-free media, iPSC CM is highly enriched with αKlotho at a concentration up to more than 10-fold of that in normal serum. αKlotho is an essential antioxidative cell maintenance and protective factor and an activator of the Nrf2 network. Immunodepletion of αKlotho reduced iPSC CM-mediated cytoprotection by ∼50%. Thus, the abundant αKlotho content significantly contributes to iPSC-mediated antioxidation and cytoprotection. Results uncover a major mechanism of iPSC action, suggest a fundamental role of αKlotho in iPSC maintenance, and support the translational potential of airway delivery of cell-free iPSC secretome for protection against lung injury. The targeted cell-free secretome-based approach may also be applicable to the amelioration of injury in other organs. Stem Cells 2017