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排序方式: 共有1165条查询结果,搜索用时 15 毫秒
91.
92.
Stochastic gene expression in a single cell 总被引:1,自引:0,他引:1
93.
Antigen bias in T cell cross-priming 总被引:1,自引:0,他引:1
Wolkers MC Brouwenstijn N Bakker AH Toebes M Schumacher TN 《Science (New York, N.Y.)》2004,304(5675):1314-1317
Activated CD8+ T cells detect virally infected cells and tumor cells by recognition of major histocompatibility complex class I-bound peptides derived from degraded, endogenously produced proteins. In contrast, CD8+ T cell activation often occurs through interaction with specialized antigen-presenting cells displaying peptides acquired from an exogenous cellular source, a process termed cross-priming. Here, we observed a marked inefficiency in exogenous presentation of epitopes derived from signal sequences in mouse models. These data indicate that certain virus- and tumor-associated antigens may not be detected by CD8+ T cells because of impaired cross-priming. Such differences in the ability to cross-present antigens should form important considerations in vaccine design. 相似文献
94.
The atomic structure of Mengo virus at 3.0 A resolution 总被引:57,自引:0,他引:57
M Luo G Vriend G Kamer I Minor E Arnold M G Rossmann U Boege D G Scraba G M Duke A C Palmenberg 《Science (New York, N.Y.)》1987,235(4785):182-191
The structure of Mengo virus, a representative member of the cardio picornaviruses, is substantially different from the structures of rhino- and polioviruses. The structure of Mengo virus was solved with the use of human rhinovirus 14 as an 8 A resolution structural approximation. Phase information was then extended to 3 A resolution by use of the icosahedral symmetry. This procedure gives promise that many other virus structures also can be determined without the use of the isomorphous replacement technique. Although the organization of the major capsid proteins VP1, VP2, and VP3 of Mengo virus is essentially the same as in rhino- and polioviruses, large insertions and deletions, mostly in VP1, radically alter the surface features. In particular, the putative receptor binding "canyon" of human rhinovirus 14 becomes a deep "pit" in Mengo virus because of polypeptide insertions in VP1 that fill part of the canyon. The minor capsid peptide, VP4, is completely internal in Mengo virus, but its association with the other capsid proteins is substantially different from that in rhino- or poliovirus. However, its carboxyl terminus is located at a position similar to that in human rhinovirus 14 and poliovirus, suggesting the same autocatalytic cleavage of VP0 to VP4 and VP2 takes place during assembly in all these picornaviruses. 相似文献
95.
The construction of multicellular organisms depends on stem cells-cells that can both regenerate and produce daughter cells that undergo differentiation. Here, we show that the gaseous messenger ethylene modulates cell division in the cells of the quiescent center, which act as a source of stem cells in the seedling root. The cells formed through these ethylene-induced divisions express quiescent center-specific genes and can repress differentiation of surrounding initial cells, showing that quiescence is not required for these cells to signal to adjacent stem cells. We propose that ethylene is part of a signaling pathway that modulates cell division in the quiescent center in the stem cell niche during the postembryonic development of the root system. 相似文献
96.
After adult zebra finches (Poephila guttata) received injections of tritiated testosterone, fewer hormone-concentrating cells were found in females than in males in two brain regions involved in song: hyperstriatum ventrale pars caudale and magnocellular nucleus of the anterior neostriatum. In some other regions, no sexual difference was detected. It is, therefore, possible that sex differences in the sensitivity of specific neural populations to hormones underlie the striking anatomical dimorphism observed in neural regions controlling song. 相似文献
97.
The US food retailing industry continues to concentrate and consolidate. Power in the agriculture, food, and nutrition system
has shifted from producers to processors, and is now shifting to retailers. Currently, only eight food-retailing corporations
control the majority of food sales in the United States. Expanding on previous research by Lyson and Raymer (2000, Agriculture and Human Values 17: 199–208), this paper examines the characteristics of the boards of directors of the leading food retailing corporations
and the indirect interlocks that bind the food retailers into a corporate community.
Rachel
Schwartz
is a PhD Candidate in the Department of Development Sociology at Cornell University. Her research interests are focused on
the relationship between food retailers and food consumers in the United States, especially in regards to the construction
of the concept of “choice.”
Thomas Lyson
was Liberty Hyde Bailey Professor in the Department of Development Sociology at Cornell University. His interests included
the relationship of agriculture and food systems on community economic development and population health. His most recent
book, Civic Agriculture, developed a problem-solving model for food and agriculture issues. Dr. Lyson passed away in December
2006. 相似文献
98.
Morrow EM Yoo SY Flavell SW Kim TK Lin Y Hill RS Mukaddes NM Balkhy S Gascon G Hashmi A Al-Saad S Ware J Joseph RM Greenblatt R Gleason D Ertelt JA Apse KA Bodell A Partlow JN Barry B Yao H Markianos K Ferland RJ Greenberg ME Walsh CA 《Science (New York, N.Y.)》2008,321(5886):218-223
To find inherited causes of autism-spectrum disorders, we studied families in which parents share ancestors, enhancing the role of inherited factors. We mapped several loci, some containing large, inherited, homozygous deletions that are likely mutations. The largest deletions implicated genes, including PCDH10 (protocadherin 10) and DIA1 (deleted in autism1, or c3orf58), whose level of expression changes in response to neuronal activity, a marker of genes involved in synaptic changes that underlie learning. A subset of genes, including NHE9 (Na+/H+ exchanger 9), showed additional potential mutations in patients with unrelated parents. Our findings highlight the utility of "homozygosity mapping" in heterogeneous disorders like autism but also suggest that defective regulation of gene expression after neural activity may be a mechanism common to seemingly diverse autism mutations. 相似文献
99.
100.