The influence of the synoptic regime on stable water isotopes in precipitation at Dome C, East Antarctica

Abstract. The correct derivation of paleotemperatures from ice cores requires exact knowledge of all processes involved before and after the deposition of snow and the subsequent formation of ice. At the Antarctic deep ice core drilling site Dome C, a unique data set of daily precipitation amount, type, and stable water isotope ratios is available that enables us to study in detail atmospheric processes that influence the stable water isotope ratio of precipitation. Meteorological data from both automatic weather station and a mesoscale atmospheric model were used to investigate how different atmospheric flow patterns determine the precipitation parameters. A classification of synoptic situations that cause precipitation at Dome C was established and, together with back-trajectory calculations, was utilized to estimate moisture source areas. With the resulting source area conditions (wind speed, sea surface temperature, and relative humidity) as input, the precipitation stable isotopic composition was modeled using the so-called Mixed Cloud Isotope Model (MCIM). The model generally underestimates the depletion of 18O in precipitation, which was not improved by using condensation temperature rather than inversion temperature. Contrary to the assumption widely used in ice core studies, a more northern moisture source does not necessarily mean stronger isotopic fractionation. This is due to the fact that snowfall events at Dome C are often associated with warm air advection due to amplification of planetary waves, which considerably increases the site temperature and thus reduces the temperature difference between source area and deposition site. In addition, no correlation was found between relative humidity at the moisture source and the deuterium excess in precipitation. The significant difference in the isotopic signal of hoarfrost and diamond dust was shown to disappear after removal of seasonality. This study confirms the results of an earlier study carried out at Dome Fuji with a shorter data set using the same methods

Three-year monitoring of stable isotopes of precipitation at Concordia Station, East Antarctica

Past temperature reconstructions from Antarctic ice cores require a good quantification and understanding of the relationship between snow isotopic composition and 2m air or inversion (condensation) temperature. Here, we focus on the French-Italian Concordia Station, central East Antarctic plateau, where the European Project for Ice Coring in Antarctica (EPICA) Dome C ice cores were drilled. We provide a multi-year record of daily precipitation types identified from crystal morphologies, daily precipitation amounts and isotopic composition. Our sampling period (2008-2010) encompasses a warmer year (2009, +1.2 degrees C with respect to 2m air temperature long-term average 1996-2010), with larger total precipitation and snowfall amounts (14 and 76% above sampling period average, respectively), and a colder and drier year (2010, -1.8 degrees C, 4% below long-term and sampling period averages, respectively) with larger diamond dust amounts (49% above sampling period average). Relationships between local meteorological data and precipitation isotopic composition are investigated at daily, monthly and inter-annual scale, and for the different types of precipitation. Water stable isotopes are more closely related to 2m air temperature than to inversion temperature at all timescales (e.g. R-2 = 03 and 0.44, respectively for daily values). The slope of the temporal relationship between daily delta O-18 and 2m air temperature is approximately 2 times smaller (0.49 parts per thousand degrees C-1) than the average Antarctic spatial (0.8 parts per thousand degrees C-1) relationship initially used for the interpretation of EPICA Dome C records. In accordance with results from precipitation monitoring at Vostok and Dome F, deuterium excess is anticorrelated with delta O-18 at daily and monthly scales, reaching maximum values in winter. Hoar frost precipitation samples have a specific fingerprint with more depleted delta O-18 (about 5% below average) and higher deuterium excess (about 8% above average) values than other precipitation types. These datasets provide a basis for comparison with shallow ice core records, to investigate post-deposition effects. A preliminary comparison between observations and precipitation from the European Centre for Medium-RangeWeather Forecasts (ECMWF) reanalysis and the simulated water stable isotopes from the Laboratoire de Meteorologie Dynamique Zoom atmospheric general circulation model (LMDZiso) shows that models do correctly capture the amount of precipitation as well as more than 50% of the variance of the observed delta O-18, driven by large-scale weather patterns. Despite a warm bias and an underestimation of the variance in water stable isotopes, LMDZiso correctly captures these relationships between delta O-18, 2m air temperature and deuterium excess. Our dataset is therefore available for further in-depth model evaluation at the synoptic scale

Serum Levels of Classical HLA Class I Antigen in HIV-Infected patients during antiretroviral therapy. Correlation with the clinical outcome

Aim. Human major histocompatibility complex class I antigens (HLA-A, -B, and -C) are heterodimetric molecules composed of a heavy chain non covalently associated with an invariant protein known as B2-microglobulin. Besides being expressed on the membrane of the large majority of nucleated cells, HLA class I antigens are found in serum (sHLA-I). We have previously detected a significant increase in the serum level of B2-microglobulin-associated HLA-I antigens in HIV-infected patients as compared to HIV-negative controls. Materials and methods. The introduction of the Highly Active Antiretroviral Theraphy (HAART) has modified the clinical course of the disease and decreased the AIDS-related morbidity and mortality. Therefore, we measured the levels of sHLA-I antigens in 64 HIV-infected patients before and during HAART treatment and correlated them with the imunological and virological response to the antiretroviral treatment. Result and conclusions. Serum sHLA-I antigen level was elevaed in all HIV-infected subjects before and significantly decreased after 36 months of HAART treatment correlated with the decrease of plasma HIV-RNA level and with the increased od CD4+ T-lymphocyte number. These results suggest that the measurement of sHLA-I antigens serum level might represent a useful surrogate marker to monitor HIV-positive subjects undergoing HAART treatment

Serum Levels of Classical HLA Class I Antigen in HIV-Infected patients during antiretroviral therapy. Correlation with the clinical outcome

Aim. Human major histocompatibility complex class I antigens (HLA-A, -B, and -C) are heterodimetric molecules composed of a heavy chain non covalently associated with an invariant protein known as B2-microglobulin. Besides being expressed on the membrane of the large majority of nucleated cells, HLA class I antigens are found in serum (sHLA-I). We have previously detected a significant increase in the serum level of B2-microglobulin-associated HLA-I antigens in HIV-infected patients as compared to HIV-negative controls. Materials and methods. The introduction of the Highly Active Antiretroviral Theraphy (HAART) has modified the clinical course of the disease and decreased the AIDS-related morbidity and mortality. Therefore, we measured the levels of sHLA-I antigens in 64 HIV-infected patients before and during HAART treatment and correlated them with the imunological and virological response to the antiretroviral treatment. Result and conclusions. Serum sHLA-I antigen level was elevaed in all HIV-infected subjects before and significantly decreased after 36 months of HAART treatment correlated with the decrease of plasma HIV-RNA level and with the increased od CD4+ T-lymphocyte number. These results suggest that the measurement of sHLA-I antigens serum level might represent a useful surrogate marker to monitor HIV-positive subjects undergoing HAART treatment

Soluble HLA G serum levels in patients with the Acquired Immunodeficiency Syndrome affected by different AIDS-defining conditions before and after anti-retrovirel treatment

We have previously reported that serum levels of soluble HLA-A, -B, -C and -G antigens are elevated in HIV-infected subjects and decrease after antiretroviral theraphy. In this study we measured soluble HLA-G serum levels in patients with AIDIS affected by different AIDIS-defining conditions before and during antiretroviral therapy and correlated them with virological and immunological parameters. Soluble HLA-G levels were significantly higher in AIDIS patients before treatment as compared to healthy controls and signifacantly decreased after 36 months of theraphy, correlating with the decrease of plasma HIV-RNA level and CD8+ T-lymphocytes number and with the increase of CD4+ T-lymphocytes number. Soluble HLA-G levels were significantly higher in patients with opportunistic infections and Kaposi's sarcoma as compared with those with wasting syndrome. These data suggest that infections and neoplasms may trigger the shedding of soluble HLA-G in serum might represent a surrogate marker to monitor virological response and immune reconstitution in HIV-positive subjects

Endothelial dysfunction in rheumatic autoimmune diseases.

Rheumatic autoimmune diseases have been associated with accelerated atherosclerosis and various types of vasculopathies. Atherosclerosis is an inflammatory condition which starts as a \u201cresponse to injury\u201d favoring endothelial dysfunction which is associated with increased expression of adhesion molecules, pro-inflammatory cytokines, pro-thrombotic factors, oxidative stress upregulation and abnormal vascular tone modulation. Endothelial dysfunction in rheumatic autoimmune diseases involves innate immune responses, including macrophages and dendritic cells expression of scavenger and toll-like receptors for modified or native LDL as well as neutrophil and complement activation, and dysregulation of adaptive immune responses, including proliferation of autoreactive T-helper-1 lymphocytes and defective function of dendritic and regulatory T cells. Specific differences for endothelial function among different disorders include: a) increased amounts of pro-atherogenic hormones, decreased amounts of anti-atherogenic hormones and increased insulin resistance in rheumatoid arthritis; b) autoantibodies production in systemic lupus erythematosus and antiphospholipid syndrome; c) smooth muscle cells proliferation, destruction of internal elastic lamina, fibrosis and coagulation and fibrinolytic system dysfunction in systemic sclerosis. Several self-antigens (i.e. high density lipoproteins, heat shock proteins, \u3b22-glycoprotein1) and self-molecules modified by oxidative events (i.e. low density lipoproteins and oxidized hemoglobin) have been identified as targets of autoimmune responses. Endothelial dysfunction leads to accelerated atherosclerosis in rheumatoid arthritis, systemic lupus erythematosus and spondyloarthropaties whereas obliterative vasculopathy is associated with systemic sclerosis. In this paper, we will briefly review the most relevant information upon endothelial dysfunction and inflammatory mechanisms in atherosclerosis and we will summarize the similarities and differences in vascular disease patterns underlying different rheumatic autoimmune diseases