| 2811. |
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| 2812. |
- Linz, Bodo, et al.
(författare)
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An African origin for the intimate association between humans and Helicobacter pylori
- 2007
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 445:7130, s. 915-918
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Tidskriftsartikel (refereegranskat)abstract
- Infection of the stomach by Helicobacter pylori is ubiquitous among humans. However, although H. pylori strains from different geographic areas are associated with clear phylogeographic differentiation(1-4), the age of an association between these bacteria with humans remains highly controversial(5,6). Here we show, using sequences from a large data set of bacterial strains that, as in humans, genetic diversity in H. pylori decreases with geographic distance from east Africa, the cradle of modern humans. We also observe similar clines of genetic isolation by distance (IBD) for both H. pylori and its human host at a worldwide scale. Like humans, simulations indicate that H. pylori seems to have spread from east Africa around 58,000 yr ago. Even at more restricted geographic scales, where IBD tends to become blurred, principal component clines in H. pylori from Europe strongly resemble the classical clines for Europeans described by Cavalli-Sforza and colleagues(7). Taken together, our results establish that anatomically modern humans were already infected by H. pylori before their migrations from Africa and demonstrate that H. pylori has remained intimately associated with their human host populations ever since.
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| 2813. |
- Liu, AQ, et al.
(författare)
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Leukotriene B4 activates T cells that inhibit B-cell proliferation in EBV-infected cord blood-derived mononuclear cell cultures
- 2008
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Ingår i: Blood. - : American Society of Hematology. - 0006-4971 .- 1528-0020. ; 111:5, s. 2693-2703
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Tidskriftsartikel (refereegranskat)abstract
- Epstein-Barr virus (EBV)–specific cellular memory is not transferred from mother to child. Therefore, EBV-induced B-cell proliferation in in vitro–infected cord blood mononuclear cell cultures is not inhibited. However, by addition of immunomodulators, polysaccharide K (PSK) or truncated thioredoxin (Trx80) that activate monocytes, EBV-specific T-cell response could be generated in such cultures. Presently, we demonstrate that leukotriene B4 (LTB4) is involved in the effect of the immunomodulators. LTB4 was detected in the medium, and T-cell activation was compromised by addition of leukotriene biosynthesis inhibitors. Moreover, we found that LTB4 added to infected cultures, which did not receive the immunomodulators, induced functional activation of the T cells. LTB4 activated the monocytes and acted directly on the T cells. In consequence, addition of LTB4 inhibited the EBV-induced proliferation of B lymphocytes. Specific cytotoxicity could be generated by restimulation of the T cells. The experiments showed successive stages of T-cell activation in acquisition of their immunologic effector function. This is orchestrated by complex cellular interactions, and autocrine loops mediated by soluble factors—here interferon (IFN)-γ, interleukin (IL)-15, IL-12, and LTB4. Importantly, the results indicate that endogenous LTB4 can induce T-cell activation that inhibits the EBV-induced proliferation of B lymphocytes.
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| 2814. |
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| 2815. |
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| 2816. |
- Liu, Cong, et al.
(författare)
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Ambient Particulate Air Pollution and Daily Mortality in 652 Cities
- 2019
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Ingår i: New England Journal of Medicine. - Waltham : Massachusetts Medical Society. - 0028-4793 .- 1533-4406. ; 381:8, s. 705-715
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: The systematic evaluation of the results of time-series studies of air pollution is challenged by differences in model specification and publication bias.METHODS: We evaluated the associations of inhalable particulate matter (PM) with an aerodynamic diameter of 10 μm or less (PM10) and fine PM with an aerodynamic diameter of 2.5 μm or less (PM2.5) with daily all-cause, cardiovascular, and respiratory mortality across multiple countries or regions. Daily data on mortality and air pollution were collected from 652 cities in 24 countries or regions. We used overdispersed generalized additive models with random-effects meta-analysis to investigate the associations. Two-pollutant models were fitted to test the robustness of the associations. Concentration-response curves from each city were pooled to allow global estimates to be derived.RESULTS: On average, an increase of 10 μg per cubic meter in the 2-day moving average of PM10 concentration, which represents the average over the current and previous day, was associated with increases of 0.44% (95% confidence interval [CI], 0.39 to 0.50) in daily all-cause mortality, 0.36% (95% CI, 0.30 to 0.43) in daily cardiovascular mortality, and 0.47% (95% CI, 0.35 to 0.58) in daily respiratory mortality. The corresponding increases in daily mortality for the same change in PM2.5 concentration were 0.68% (95% CI, 0.59 to 0.77), 0.55% (95% CI, 0.45 to 0.66), and 0.74% (95% CI, 0.53 to 0.95). These associations remained significant after adjustment for gaseous pollutants. Associations were stronger in locations with lower annual mean PM concentrations and higher annual mean temperatures. The pooled concentration-response curves showed a consistent increase in daily mortality with increasing PM concentration, with steeper slopes at lower PM concentrations.CONCLUSIONS: Our data show independent associations between short-term exposure to PM10 and PM2.5 and daily all-cause, cardiovascular, and respiratory mortality in more than 600 cities across the globe. These data reinforce the evidence of a link between mortality and PM concentration established in regional and local studies. (Funded by the National Natural Science Foundation of China and others.).
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| 2817. |
- Liu, CY, et al.
(författare)
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Impact of disease-modifying therapy on dendritic cells and exploring their immunotherapeutic potential in multiple sclerosis
- 2022
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Ingår i: Journal of neuroinflammation. - : Springer Science and Business Media LLC. - 1742-2094. ; 19:1, s. 298-
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Tidskriftsartikel (refereegranskat)abstract
- Dendritic cells (DCs) are the most potent professional antigen-presenting cells (APCs), which play a pivotal role in inducing either inflammatory or tolerogenic response based on their subtypes and environmental signals. Emerging evidence indicates that DCs are critical for initiation and progression of autoimmune diseases, including multiple sclerosis (MS). Current disease-modifying therapies (DMT) for MS can significantly affect DCs’ functions. However, the study on the impact of DMT on DCs is rare, unlike T and B lymphocytes that are the most commonly discussed targets of these therapies. Induction of tolerogenic DCs (tolDCs) with powerful therapeutic potential has been well-established to combat autoimmune responses in laboratory models and early clinical trials. In contrast to in vitro tolDC induction, in vivo elicitation by specifically targeting multiple cell-surface receptors has shown greater promise with more advantages. Here, we summarize the role of DCs in governing immune tolerance and in the process of initiating and perpetuating MS as well as the effects of current DMT drugs on DCs. We then highlight the most promising cell-surface receptors expressed on DCs currently being explored as the viable pharmacological targets through antigen delivery to generate tolDCs in vivo.
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| 2818. |
- Liu, C. M., et al.
(författare)
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Electron-Scale Measurements of Dipolarization Front
- 2018
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Ingår i: Geophysical Research Letters. - : AMER GEOPHYSICAL UNION. - 0094-8276 .- 1944-8007. ; 45:10, s. 4628-4638
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Tidskriftsartikel (refereegranskat)abstract
- Dipolarization front (DF)-a sharp boundary with scale of ion inertial length (c/omega(pi)) in the Earth's magnetotail-can also have fine structures at electron scale (c/omega(pe)). Such electron-scale structures, determining the local energy conversion, have not been revealed by multispacecraft observations so far, due to the large separation of spacecraft in previous studies. Here we report the first electron-scale multispacecraft measurements of DF, using data from the recent Magnetospheric Multiscale mission. We find strong parallel currents only in the high-density side of the DF but strong perpendicular currents across the whole DF. We find no parallel electric fields during the DF interval. Although DF is primarily an energy-load region (E.J > 0), the electron-scale currents could lead to a localized energy generation (E.J < 0). Such features are different from those reported in previous multispacecraft studies, where the currents, electric fields, and energy conversion are uniform across the DF; they also shed lights on the study of substorm current wedge, which is crucial in the magnetosphere-ionosphere coupling.
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| 2819. |
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| 2820. |
- Liu, C. P., et al.
(författare)
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High-Speed 1.56-μm Multiple Quantum Well Asymmetric Fabry-Perot Modulator/Detector (AFPMD) for Radio-Over-Fibre Applications
- 2005
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Ingår i: Microwave Photonics, 2005. MWP 2005. International Topical Meeting on. - : IEEE. ; , s. 137-140
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Konferensbidrag (refereegranskat)abstract
- We have designed and fabricated air-bridged optical modulator/detectors with modulation bandwidth exceeding 15GHz, the highest yet reported for InGaAsP/InGaAsP MQW AFPMDs. Wavelength dependence of the modulated output power at microwave frequencies is reported for the first time and the wide optical bandwidths ( gt; 17nm) so measured suggest that the AFPMD can be used with low-cost uncooled CWDM lasers in radio-over-fibre applications.
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