CD43 is a major heavily glycosylated lymphocyte surface molecule. It has been shown to play an important role in lymphocyte activation and cell-cell interactions. Here we demonstrate that in human ...activated lymphocytes and CEM T cells, CD43 is a sulfated molecule. We also observed that CD45, another lymphocyte surface glycoprotein, is a sulfated molecule. 35SO4(2-) incorporation would thus appear to be an appropriate labeling method for CD43 and CD45 visualization. Moreover, we show that the level of cell surface protein sulfation can modulate CD43-mediated homotypic aggregation induced by CD43 monoclonal antibodies. It is well known that glycoprotein sulfation is required for various recognition phenomena. Since there are numerous potential sulfation sites on CD43 and CD45, these residues could play an important role in regulating cell-cell interactions.
Complementary DNA encoding a human Gal(β1‐3)GalNAc α2,3‐sialyltransferase type II (hST3Gal II) was cloned from a CEM T‐cell cDNA library using a 23‐base oligonucleotide probe. The sequence of this ...probe was established on the basis of a slightly divergent sialylmotif L that was obtained by polymerase chain reaction with degenerate oligonucleotide primers based on the conserved sialylmotif L of mammalian Gal(β1‐3)GalNAc α2,3‐sialyltransferases. It was thus confirmed that a short oligonucleotide probe may be sensitive and highly specific. The nucleotide and amino acid sequences of hST3Gal II show, respectively, 56.3% and 49.3% similarity to hST3Gal I Kitagawa, H. & Paulson, J. C. (1994) J. Biol. Chem. 269, 17872–17878 and 88.1% and 93.7% similarity to inurine ST3Gal II Lee, Y. C., Kojima, N., Wada, E., Kurosawa, N., Nakaoka, T., Hamamoto, T. & Tsuji, S. (1994) J. Biol. Chem. 269, 10028–10033. hST3Gal II mRNA was highly expressed in heart, liver, skeletal muscle and various lymphoid tissues but not in brain and kidney. A soluble form of hST3Gal II expressed in COS‐7 cells was tested in vitro for substrate specificity and kinetic properties. Asialofetuin and asialo‐bovine submaxillary mucin appeared better substrates for hST3Gal II than for its murine counterpart as previously reported Kojima, N., Lee, Y.‐C., Hamamoto, X, Kurosawa, N. & Tsuji, S. (1994) Biochemistry 33, 5772–57761. In previous studies, we have shown hyposialylation of O‐glycans attached to two major lymphocyte CD43 and CD45 cell surface molecules in human‐immunodeficiency‐virus‐1(H1V‐1) –infected T‐cell lines. Since comparable levels of hST3Gal 1 and hST3Gal II mRNA and enzymatic activity were observed in parental and HIV‐1‐infected CEM T‐cell lysates, the sialylation defect associated with HIV infection of this cell line is probably due to a mechanism different from a simple altered catalytic activity of these sialyltransferases.
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BFBNIB, DOBA, FZAB, GIS, IJS, IZUM, KILJ, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBMB, SIK, UILJ, UKNU, UL, UM, UPUK
The synthesis of Galalpha1-3Gal-terminated oligosaccharides (alpha-Gal) epitopes has been interrupted during the course of evolution, starting with Old World primates. Partial sequences similar to ...the alpha1,3-galactosyltransferase (alpha1,3GalT) gene, which governs the synthesis of alpha-Gal epitopes, have been detected in the human genome and were found to correspond to pseudogenes. We completed the sequence of the human alpha1,3GalT pseudogene present on chromosome 9 and found it to be organized like the murine alpha1,3GalT gene. In human cell lines and several normal and tumor tissues we detected truncated transcripts corresponding to this pseudogene. Considering these mRNAs, translation of an open reading frame containing the first four translated exons but missing the two catalytic exons could predict a truncated alpha1,3GalT polypeptide that should be enzymatically inactive. We show that transcription of human alpha1,3GalT is prematurely terminated at the level of a strong transcriptional stop signal in the middle of intron VII. We were able to reproduce this effect in vitro by subcloning the implicated DNA region upstream from a reporter cDNA. The premature transcriptional arrest of human alpha1,3-GalT gene leads to an ectopic splicing event and to the connection of a short intronic sequence downstream from translated exons. Finally, we show that these truncated transcripts are overexpressed in cell lines with modifications of O-glycans.
Cucchiarini et al provide evidence that the mutated CD4 is always expressed in HIV-1-, and HIV-2-infected cells, independent of the presence of Nef, while the endogenous CD4 is completely lost.
•A complete spectral in-flight calibration of NOMAD is presented.•A model to compute spectral continuum is produced as a function of instrument properties.•NOMAD sensitivity to atmospheric CH4 is ...evaluated with different aerosol loads.•NOMAD sensitivity to CH4 in Solar Occultation is on sub-ppbv level.•NOMAD will be able to trace seasonal trends for CH4 with nadir observations.
The Nadir and Occultation for MArs Discovery instrument (NOMAD), onboard the ExoMars Trace Gas Orbiter (TGO) spacecraft was conceived to observe Mars in solar occultation, nadir, and limb geometries, and will be able to produce an outstanding amount of diverse data, mostly focused on properties of the atmosphere. The infrared channels of the instrument operate by combining an echelle grating spectrometer with an Acousto-Optical Tunable Filter (AOTF). Using in-flight data, we characterized the instrument performance and parameterized its calibration. In particular: an accurate frequency calibration was achieved, together with its variability due to thermal effects on the grating. The AOTF properties and transfer function were also quantified, and we developed and tested a realistic method to compute the spectral continuum transmitted through the coupled grating and AOTF system. The calibration results enabled unprecedented insights into the important problem of the sensitivity of NOMAD to methane abundances in the atmosphere. We also deeply characterized its performance under realistic conditions of varying aerosol abundances, diverse albedos and changing illumination conditions as foreseen over the nominal mission. The results show that, in low aerosol conditions, NOMAD single spectrum, 1σ sensitivity to CH4 is around 0.33 ppbv at 20 km of altitude when performing solar occultations, and better than 1 ppbv below 30 km. In dusty conditions, we show that the sensitivity drops to 0 below 10 km. In Nadir geometry, results demonstrate that NOMAD will be able to produce seasonal maps of CH4 with a sensitivity around 5 ppbv over most of planet's surface with spatial integration over 5 × 5° bins. Results show also that such numbers can be improved by a factor of ~10 to ~30 by data binning. Overall, our results quantify NOMAD's capability to address the variable aspects of Martian climate.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
It has been suggested that dust storms efficiently transport water vapor from the near‐surface to the middle atmosphere on Mars. Knowledge of the water vapor vertical profile during dust storms is ...important to understand water escape. During Martian Year 34, two dust storms occurred on Mars: a global dust storm (June to mid‐September 2018) and a regional storm (January 2019). Here we present water vapor vertical profiles in the periods of the two dust storms (Ls = 162–260° and Ls = 298–345°) from the solar occultation measurements by Nadir and Occultation for Mars Discovery (NOMAD) onboard ExoMars Trace Gas Orbiter (TGO). We show a significant increase of water vapor abundance in the middle atmosphere (40–100 km) during the global dust storm. The water enhancement rapidly occurs following the onset of the storm (Ls~190°) and has a peak at the most active period (Ls~200°). Water vapor reaches very high altitudes (up to 100 km) with a volume mixing ratio of ~50 ppm. The water vapor abundance in the middle atmosphere shows high values consistently at 60°S‐60°N at the growth phase of the dust storm (Ls = 195°–220°), and peaks at latitudes greater than 60°S at the decay phase (Ls = 220°–260°). This is explained by the seasonal change of meridional circulation: from equinoctial Hadley circulation (two cells) to the solstitial one (a single pole‐to‐pole cell). We also find a conspicuous increase of water vapor density in the middle atmosphere at the period of the regional dust storm (Ls = 322–327°), in particular at latitudes greater than 60°S.
Plain Language Summary
The most striking phenomenon on Mars is a planet‐encircling storm, “global dust storm.” Once it starts, the floating dust covers the whole atmosphere for more than several weeks. Recent studies suggest that dust storms effectively transport water vapor from the near‐surface to the middle atmosphere. In June to September 2018 and January 2019, a strong global dust storm and a regional storm occurred on Mars, respectively. This study investigates altitude profiles of water vapor in the Mars atmosphere measured during the dust storms, by using brand‐new measurements by Nadir and Occultation for Mars Discovery onboard the ExoMars Trace Gas Orbiter. We confirm that the water vapor expanded into the middle atmosphere, and we find that the water vapor reached very high altitudes (up to 100 km) during the dust storms. The dust storms intensify the atmospheric dynamics and heat the atmosphere. As a result, water vapor is lifted to higher altitudes and distributes along the meridional circulation.
Key Points
We present vertical profiles of water vapor in the Martian atmosphere during global and regional dust storms in 2018‐2019
We show a rapid and significant increase of water vapor in the middle atmosphere (40‐100 km) during both global and regional dust storms
Water vapor reaches very high altitudes, at least around 100 km, during the global dust storm
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
NOMAD is a suite of three spectrometers that will be launched in 2016 as part of the joint ESA-Roscosmos ExoMars Trace Gas Orbiter mission. The instrument contains three channels that cover the IR ...and UV spectral ranges and can perform solar occultation, nadir and limb observations, to detect and map a wide variety of Martian atmospheric gases and trace species. Part I of this work described the models of the UVIS channel; in this second part, we present the optical models representing the two IR channels, SO (Solar Occultation) and LNO (Limb, Nadir and Occultation), and use them to determine signal to noise ratios (SNRs) for many expected observational cases. In solar occultation mode, both the SO and LNO channel exhibit very high SNRs >5000. SNRs of around 100 were found for the LNO channel in nadir mode, depending on the atmospheric conditions, Martian surface properties, and observation geometry.
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