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排序方式: 共有80条查询结果,搜索用时 15 毫秒
1.
Biological Invasions - Multidimensional niche differentiation might increase the stability of coexistence by reducing overall niche overlap which might have implications on the dynamics of... 相似文献
2.
Ruf IK Rhyne PW Yang H Borza CM Hutt-Fletcher LM Cleveland JL Sample JT 《Molecular and cellular biology》1999,19(3):1651-1660
Loss of the Epstein-Barr virus (EBV) genome from Akata Burkitt lymphoma (BL) cells is coincident with a loss of malignant phenotype, despite the fact that Akata and other EBV-positive BL cells express a restricted set of EBV gene products (type I latency) that are not known to overtly affect cell growth. Here we demonstrate that reestablishment of type I latency in EBV-negative Akata cells restores tumorigenicity and that tumorigenic potential correlates with an increased resistance to apoptosis under growth-limiting conditions. The antiapoptotic effect of EBV was associated with a higher level of Bcl-2 expression and an EBV-dependent decrease in steady-state levels of c-MYC protein. Although the EBV EBNA-1 protein is expressed in all EBV-associated tumors and is reported to have oncogenic potential, enforced expression of EBNA-1 alone in EBV-negative Akata cells failed to restore tumorigenicity or EBV-dependent down-regulation of c-MYC. These data provide direct evidence that EBV contributes to the tumorigenic potential of Burkitt lymphoma and suggest a novel model whereby a restricted latency program of EBV promotes B-cell survival, and thus virus persistence within an immune host, by selectively targeting the expression of c-MYC. 相似文献
3.
Alternate replication in B cells and epithelial cells switches tropism of Epstein-Barr virus 总被引:13,自引:0,他引:13
Epstein-Barr virus is ubiquitous and is causally implicated in lymphoid and epithelial malignancies. Virus invades oropharyngeal mucosa and establishes latency in B lymphocytes. Reactivating lymphocytes shed virus into saliva for spread to new hosts. A complex of three virus glycoproteins, gH, gL and gp42, is essential for entry. B-cell entry requires binding of gp42 to human leukocyte antigen (HLA) class II whereas entry into epithelial cells lacking HLA class II requires complexes without gp42. To accommodate infection of each, the virus carries both three-part and two-part complexes. We show here that HLA class II in the virus-producing cell alters the ratio of three-part to two-part complexes. As a consequence, virus originating in epithelial cells efficiently infects B cells whereas B-cell derived virus better infects epithelial cells. This molecular switch is a novel strategy that could alter tropism of virus from epithelium to B cells and then back to epithelium in a new host. 相似文献
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5.
G Benga O Popescu V Borza A Hodarn?u V I Pop J Wrigglesworth 《Biochimica et biophysica acta》1991,1061(2):309-312
The water diffusional permeability of human red blood cells following exposure to various sulfhydryl group (SH) reagents have been studied using a nuclear magnetic resonance technique. Exposure of red blood cells up to 12 mM N-ethylmaleimide (NEM) or 10 mM 5,5'-dithio-bis(2-nitrobenzoic acid) (DTNE) alone does not affect water diffusion. In contrast, when DTNB treatment follows a preincubation of the cells with NEM, a small (18% at 37 degrees C) but significant inhibition of water permeability occurs. The NEM and DTNB treatment of the cells caused no change of the cell shape and volume or of the cell water volume. Consequently, the inhibition observed after NEM and DTNB treatment has a real significance. 相似文献
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René Molinier Br.-Bl. C. Vanden Berghen Al. Borza N. Boscaiu T. Wraber 《Plant Ecology》1963,11(5-6):401-411
Sans résumé 相似文献
8.
A L. Borza 《Plant Ecology》1958,8(3):181-188
Ohne Zusammenfassung 相似文献
9.
Histones of the green alga Chlamydomonas reinhardtii were prepared by a new method and fractionated by reversed-phase high-performance liquid chromatography. Acid-urea-Triton gel analysis and tritiated acetate labeling demonstrated high levels of steady-state acetylation for the single histone H3 protein, in contrast to low levels on histones H4 and H2B. Twenty percent of histone H3 is subject to dynamic acetylation with, on average, three acetylated lysine residues per protein molecule. Histone synthesis in light-dark-synchronized cultures was biphasic with pattern differences between two histone H1 variants, between two H2A variants, and between H2B and ubiquitinated H2B. Automated protein sequence analysis of histone H3 demonstrated a site-specific pattern of steady-state acetylation between 7 and 17% at five of the six amino-terminal lysines and of monomethylation between 5 and 81% at five of the eight amino-terminal lysines in a pattern that may limit dynamic acetylation. An algal histone H3 sequence was confirmed by protein sequencing with a single threonine as residue 28 instead of the serine28-alanine29 sequence, present in all other known plant and animal H3 histones. 相似文献
10.
Gheorghe Benga Victoria Borza Octavian Popescu Victor I. Pop Ana Mureşan 《The Journal of membrane biology》1986,89(2):127-130
Summary The water diffusion across human erythrocyte membrane has been studied on intact cells and resealed ghosts by a doping NMR technique. Although the water exchange time of ghosts was longer than that of erythrocytes, no significant differences in their diffusional permeability were noticed for temperatures in the range 2–43°C. Contrary to what was previously noticed in erythrocytes, no significant increase in the water exchange time of ghosts in the acid range of pH occurred. 相似文献