Extraordinary blowing snow transport events in East Antarctica

In the convergence slope/coastal areas of Antarctica, a large fraction of snow is continuously eroded and exported by wind to the atmosphere and into the ocean. Snow transport observations from instruments and satellite images were acquired at the wind convergence zone of Terra Nova Bay (East Antarctica) throughout 2006 and 2007. Snow transport features are well-distinguished in satellite images and can extend vertically up to 200 m as first-order quantitatively estimated by driftometer sensor FlowCapt™. Maximum snow transportation occurs in the fall and winter seasons. Snow transportation (drift/blowing) was recorded for ~80% of the time, and 20% of time recorded, the flux is >10-2 kg m-2 s-1 with particle density increasing with height. Cumulative snow transportation is ~4 orders of magnitude higher than snow precipitation at the site. An increase in wind speed and transportation (~30%) was observed in 2007, which is in agreement with a reduction in observed snow accumulation. Extensive presence of ablation surface (blue ice and wind crust) upwind and downwind of the measurement site suggest that the combine processes of blowing snow sublimation and snow transport remove up to 50% of the precipitation in the coastal and slope convergence area. These phenomena represent a major negative effect on the snow accumulation, and they are not sufficiently taken into account in studies of surface mass balance. The observed wind-driven ablation explains the inconsistency between atmospheric model precipitation and measured snow accumulation value. © 2009 The Author(s)

Three years continuous record of the Earth’s magnetic field at Concordia Station (DomeC, Antarctica)

The magnetic observatory deployed at DomeC, Antarctica, in the French-Italian base known as Concordia hasnow been permanently running for more than three years. This paper focuses on these long-term results whichare more relevant for an observatory intended to provide absolute values of the field. The problems whichemerged in this fairly long record are discussed and solutions suggested to upgrade the observatory to the standardsof an absolute one (i.e. Intermagnet standards).Mailing address: Dr. Aude Chambodut, Ecole et Observatoiredes Sciences de la Terre 5, rue Descartes 67084, StrasbourgCedex, France; e-mail: [email protected]

Stomodeal and neurohypophysial placodes in Ciona intestinalis: Insights into the origin of the pituitary gland

The ascidian larva has a central nervous system which shares basic characteristics with craniates, such as tripartite organisation and many developmental genes. One difference, at metamorphosis, is that this chordate-like nervous system regresses and the adult\u2019s neural complex, composed of the cerebral ganglion and associated neural gland, forms. It is known that neural complex differentiation involves two ectodermal structures, the neurohypophysial duct, derived from the embryonic neural tube, and the stomodeum, i.e. the rudiment of the oral siphon; nevertheless, their precise role remains to be clarified. We have shown that in Ciona intestinalis, the neural complex primordium is the neurohypophysial duct, which in the early larva is a short tube, blind anteriorly, with its lumen in continuity with that of the central nervous system, i.e. the sensory vesicle. The tube grows forwards and fuses with the posterior wall of the stomodeum, a dorsal ectodermal invagination of the larva. The duct then loses posterior communication with the sensory vesicle and begins to grow on the roof of the vesicle itself. The neurohypophysial duct differentiates into the neural gland rudiment; its dorsal wall begins to proliferate neuroblasts, which migrate and converge to build up the cerebral ganglion. The most anterior part of the neural gland organizes into the ciliated duct and funnel, whereas the most posterior part elongates and gives rise to the dorsal strand. The hypothesis that the neurohypophysial duct/stomodeum complex possesses cell populations homologous to the craniate olfactory and adenohypophysial placodes and hypothalamus is discussed

Effect of oxysterols on cell survival and proliferation pathways in human endothelial cells

Copia digital. Madrid : Ministerio de Cultura. Subdirección General de Coordinación Bibliotecaria, 200

Antiapoptotic and Proliferative Effects of Low Concentrations of 7 beta-Hydroxycholesterol in Human Endothelial Cells via ERK Activation

The atherogenic potential of oxidized low-density lipoproteins (oxLDL) has been correlated to their 7beta-hydroxycholesterol (7betaOHC) content; oxLDLs have a dual effect on endothelial cell viability, inducing apoptosis or proliferation depending on the concentration. Considering that 7betaOHC is apoptotic for endothelial cells at concentrations >/=20 mug/ml, a study on the effect of lower concentrations of 7betaOHC on human umbilical vein endothelial cells (HUVECs) was undertaken. 7betaOHC (1-10 mug/ml) increased 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide reduction of growth-factor-deprived HUVECs. This effect was due to the increased cell proliferation, determined by [(3)H]thymidine incorporation, and the reduction of apoptosis, revealed by the decreased caspase-3 activation and annexin V staining. 7betaOHC also protected against staurosporine apoptosis. 7betaOHC induced an increase in intracellular ROS antagonized by N-acetylcysteine; however, HUVECs treatment with the antioxidant did not inhibit the effects of 7betaOHC. 7betaOHC produced an increase in extracellular signal-regulated kinase (ERK) phosphorylation that was blocked by inhibitors of store-operated calcium entry 2-aminoethoxydiphenyl borate and gadolinium. MEK inhibition with PD98059 or U0126 as well as store-operated calcium entry inhibition antagonized the effect of 7betaOHC. The results suggest that 7betaOHC promotes HUVECs survival and proliferation by a mechanism independent of ROS production and involving calcium-dependent activation of ERK