排序方式: 共有22条查询结果,搜索用时 0 毫秒
21.
Benvenuti F Hugues S Walmsley M Ruf S Fetler L Popoff M Tybulewicz VL Amigorena S 《Science (New York, N.Y.)》2004,305(5687):1150-1153
Upon maturation, dendritic cells (DCs) acquire the unique ability to activate na?ve T cells. We used time-lapse video microscopy and two-photon imaging of intact lymph nodes to show that after establishing initial contact between their dendrites and na?ve T lymphocytes, mature DCs migrate toward the contacted lymphocytes. Subsequently, the DCs tightly entrap the T cells within a complex net of membrane extensions. The Rho family guanosine triphosphatases Rac1 and Rac2 but not Rho itself control the formation of dendrites in mature DCs, their polarized short-range migration toward T cells, and T cell priming. 相似文献
22.
Bretz M Beyer M Cramer B Knecht A Humpf HU 《Journal of agricultural and food chemistry》2006,54(17):6445-6451
Deoxynivalenol (DON) is a toxic secondary metabolite produced by molds of the Fusarium genus, which are able to infect cereal crops in the field. Concerning its rate of occurrence and mean concentration, DON is one of the most important mycotoxins in cereal commodities. Its toxic effects range from causing diarrhea, vomiting, and gastro-intestinal inflammation to noncompetitive inhibition of the biosynthesis of proteins in eukaryotic cells. To study the stability of DON under food-processing conditions such as cooking or baking, we performed model heating experiments and screened the residue for degradation products. Heating of DON and 3-acetyldeoxynivalenol (3-AcDON), especially under alkaline conditions, gave a mixture of compounds, which were isolated and structurally elucidated by NMR and MS experiments. Three of these compounds were already known (norDON A, norDON B, and norDON C), while four were new and named 9-hydroxymethyl DON lactone, norDON D, norDON E, and norDON F. The significance of the DON degradation products was checked by analyzing commercially available food samples. norDON A, B, and C were detected in 29-66% of the samples in mean concentrations ranging from 3 to 15 microg/kg. Furthermore, cell culture experiments using IHKE cells showed that the compounds that were detected in food samples are less cytotoxic in the formazan dye cytotoxicity assay compared to DON. Whereas DON revealed a median effective concentration (EC50) at 1.1 micromol/L, all other compounds did not show any significant effect up to 100 micromol/L. These findings indicate that the degradation of DON under thermal treatment might reduce the toxicity of DON contaminated food. 相似文献