TEC

About: TEC is a research topic. Over the lifetime, 5119 publications have been published within this topic receiving 84696 citations.

Activation and Association of the Tec Tyrosine Kinase with the Human Prolactin Receptor: Mapping of a Tec/Vav1-Receptor Binding Site

Abstract: Stimulation of the PRL receptor (PRLr) results in the activation of the guanine nucleotide exchange factor (GEF) p95 Vav1 with corresponding alterations in cytoarchitecture and cell motility. To better understand the mechanisms involved in the regulation of Vav1 activity, the role of the tyrosine kinase p70 Tec was examined. Coimmunoprecipitation and in vitro kinase assays revealed that ligand stimulation of the PRLr resulted in the rapid activation of Tec and its concomitant association with the PRLr. When coexpressed in COS-1 cells, both Vav1 and Tec were found to associate with the PRLr in the presence of ligand. In the absence of receptor, a constitutive complex between Vav1 and Tec was noted. Both Vav1 and Tec, however, were capable of independent engagement of a bipartite intracellular domain of the PRLr. Deletion mapping studies confined this interaction to residues 323 to 527 of the intracellular domain of the PRLr. Furthermore, Tec enhanced the GEF activity of Vav1 as evidenced by an increase in GTP-bound Rac1. These data would suggest a pivotal function for the formation of a Tec/Vav1/PRLr complex during PRL-driven signal transduction, given the role of Vav1 in the control of cell proliferation and the regulation of Rho family-mediated cytoskeletal alterations. (Molecular Endocrinology 15: 832‐841, 2001)

Tomographic imaging of the ionosphere over Japan by the modified truncated SVD method

Abstract: A computerized tomography technique was applied to reconstruct two-dimensional electron density distributions from measurements of total electron content (TEC). We found that the modified truncated singular value decomposition (MTSVD) method, which is usually effective in ill-posed inversion problems, is effective in the ionospheric application. Furthermore, a main control parameter for a good reconstruction was examined by using several density distribution models, and the effects of noise in TEC and discretization error were also investigated. After the simulation study, the MTSVD method was applied to actual TEC data in a magnetically disturbed period. Total electron contents were observed, at four receiving stations covering a latitudinal range of 9.7 degrees with a longitudinal range of 2.2 degrees over Japan, by using signals transmitted from a Navy Navigational Satellite System (NNSS) satellite. The tomographic reconstruction revealed a large-scale structure of electron density in the disturbed ionosphere.

A common stem cell for murine cortical and medullary thymic epithelial cells

Abstract: We have addressed the question whether the epithelial stroma in the thymus is derived from a common stem cell or whether cortical and medullary epithelial cells are derived from different embryonic stem cells emerging, for example, from endoderm and ectoderm. By the use of rapidly expanding cultures of thymic epithelial cells (TEC) from 14 to 16 day-old murine fetuses and by specific antibodies against cortical and medullary epithelium, respectively, we were able to demonstrate a small subpopulation of double-labeled TEC in the cultures. These cells were not present in TEC cultures initiated from thymuses of neonatal mice. Double-labeled TEC were also found in tissue sections from fetal thymuses. These findings may indicate that TEC populations of the cortex and the medulla are derived from a common stem cell, with potential for differentiation toward both cortical and medullary TEC.

Southern Hemisphere ionosphere and plasmasphere response to the interplanetary shock event of 29–31 October 2003

Abstract: [1] We analyze the effects on the Southern Hemisphere ionosphere and plasmasphere due to the 29–31 October 2003 geomagnetic storms (the so-called series of Halloween storms). Solar wind data from ACE and ionospheric data from the GPS (Global Position System) ground and LEO (Low Earth Orbit) receivers, the TOPEX/Poseidon altimeter, the IMAGE FUV camera, and the DMSP drift meter are used to understand the ionospheric dynamics as a function of the storm phase. The detailed structure of the ionosphere has been obtained using tomographic reconstruction applied to data from both ground- and space-based GPS receivers. The tomographic approach using LEO observations of signals received from GPS satellites above the LEO's horizon allows us to investigate the topside ionospheric and plasmaspheric density distribution in more detail than can be obtained using ground-based GPS receivers. This is because with ground-based receivers, the higher topside ionosphere and plasmasphere contribute only a small fraction to the total electron content (TEC) and so the measurements are dominated by the ionospheric structure at the F2 peak. In contrast, the Australian LEO satellite, FedSat, which has been used for this study, orbits at 800 km altitude, well above the F2 peak and hence the TEC measured is primarily due to the upper topside ionosphere and plasmasphere. This paper presents the tomographically reconstructed topside ionosphere and plasmasphere electron density distributions using LEO observations. The temporal and regional maps of TEC and the IMAGE FUV data show that the storm that commenced on 29 October dramatically decreased the plasma density in the Southern Hemisphere middle and high latitudes. The region remained depleted of plasma for more than 24 hours until 31 October, when the second severe storm began. TOPEX/Poseidon data shows a daytime localized density enhancement occurred above the middle of the Pacific Ocean. These results show large interhemispheric and longitudinally narrow storm-time structure in the ionosphere and topside ionosphere/plasmasphere.