全文获取类型
收费全文 | 77篇 |
免费 | 4篇 |
出版年
2019年 | 1篇 |
2018年 | 1篇 |
2017年 | 1篇 |
2016年 | 2篇 |
2015年 | 5篇 |
2014年 | 5篇 |
2013年 | 4篇 |
2012年 | 3篇 |
2011年 | 6篇 |
2010年 | 3篇 |
2009年 | 1篇 |
2008年 | 3篇 |
2007年 | 1篇 |
2006年 | 4篇 |
2005年 | 1篇 |
2003年 | 2篇 |
2002年 | 1篇 |
2001年 | 4篇 |
2000年 | 2篇 |
1999年 | 1篇 |
1998年 | 4篇 |
1997年 | 3篇 |
1996年 | 1篇 |
1995年 | 4篇 |
1994年 | 2篇 |
1991年 | 1篇 |
1990年 | 2篇 |
1989年 | 3篇 |
1988年 | 1篇 |
1984年 | 1篇 |
1983年 | 3篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1977年 | 1篇 |
1976年 | 1篇 |
排序方式: 共有81条查询结果,搜索用时 15 毫秒
1.
蚕豆叶片发育与衰老过程中超氧物歧化酶活性与丙二醛含量变化 总被引:2,自引:0,他引:2
蚕豆植株叶片随茎节自上而下表现出明显的发育与衰老顺序,可作为衰老特征的是叶绿素和蛋白质含量明显下降。蚕豆叶中SOD活性主要定位于12 000× g离心后所得的上清液和叶绿体组分。衰老叶片的SOD总活性和叶绿体组分的相对活性都有所下降,SOD同工酶谱也发生了改变。O_2~ 产生速率随叶龄增大而稍上升;而MDA含量在叶片外观表现枯黄衰老征兆前就急剧上升。可能因为衰老叶片过氧化氢酶活性大幅度下降与SOD之间的不平衡,致使O_2~ 代谢中间产物累积而引起膜的损伤. 相似文献
2.
Steven A. Belinsky John F. Lechner Neil F. Johnson 《In vitro cellular & developmental biology. Animal》1995,31(5):361-366
Identifying the causal events and temporal aspects of lung cancer development requires the ability to isolate target and nontarget
cells for comparative analyses. Current methodology can either isolate only one pure specific cell population from a lung
or multiple cell types at lower purity. Previous studies in our laboratory have identified the alveolar type II cell as the
progenitor cell for tumor development in the A/J mouse. The purpose of this study was to develop new protocols for the isolation
and culture of type II and Clara cells from the mouse lung. Both type II and Clara cells were obtained in high purity using
a sequential centrifugal elutriation protocol. In the first elutriation, cell fractions were collected using a Standard chamber.
The type II and Clara cell fractions were then elutriated separately (two different separations) using a Sanderson chamber.
The final purity of the type II and Clara cell preparations was 73% and 76%, respectively. Colonies of 4 to 20 Clara cells
exhibiting epithelial morphology were evident 1 wk after plating in low serum medium. The growth of type II cells required
the addition of bronchioalveolar lavage fluid and acidic fibroblast growth factor to the medium. The isolation of viable mouse
type II and Clara cells in high purity should facilitate the identification of cell-specific changes in gene expressions or
in enzymatic pathways following in vivo or in vitro exposure to environmental carcinogens. 相似文献
3.
Biosynthesis of lysosomal hydrolases: their synthesis in bound polysomes and the role of co- and post-translational processing in determining their subcellular distribution 总被引:37,自引:20,他引:17
下载免费PDF全文
![点击此处可从《The Journal of cell biology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
By in vitro translation of mRNA’s isolated from free and membrane-bound polysomes, direct evidence was obtained for the synthesis of two lysosomal hydrolases, β-glucuronidase of the rat preputial gland and cathespin D of mouse spleen, on polysomes bound to rough endoplasmic reticulum (ER) membranes. When the mRNA’s for these two proteins were translated in the presence of microsomal membranes, the in vitro synthesized polypeptides were cotranslationally glycosylated and transferred into the microsomal lumen. Polypeptides synthesized in the absence of microsomal membranes were approximately 2,000 daltons larger than the respective unglycosylated microsomal polypeptides found after short times of labeling in cultured rat liver cells treated with tunicamycin. This strongly suggests that nascent chains of the lysosomal enzymes bear transient amino terminal signals which determine synthesis on bound polysomes and are removed during the cotranslational insertion of the polypeptides into the ER membranes. In the line of cultured rat liver cells used for this work, newly synthesized lysosomal hydrolases showed a dual destination; approximately 60 percent of the microsomal polypeptides detected after short times of labeling were subsequently processed proteolytically to lower molecular weight forms characteristic of the mature enzymes. The remainder was secreted from the cells without further proteolytic processing. As previously observed by other investigations in cultured fibroblasts (A. Gonzalez-Noriega, J.H. Grubbs, V. Talkad, and W.S. Sly, 1980, J Cell Biol. 85: 839-852; A. Hasilik and E.F. Neufeld, 1980, J. Biol. Chem., 255:4937-4945.) the lysosomotropic amine chloroquine prevented the proteolytic maturation of newly synthesized hydrolases and enhanced their section. In addition, unglycosylated hydrolases synthesized in cells treated with tunicamycin were exclusively exported from the cells without undergoing proteolytic processing. These results support the notions that modified sugar residues serve as sorting out signals which address the hydrolases to their lysosomal destination and that final proteolytic cleavage of hydrolase precursors take place within lysosome itself. Structural differences in the carbohydrate chains of intracellular and secreted precursors of cathespin D were detected from their differential sensitivity to digestion with endoglycosidases H and D. These observations suggest that the hydrolases exported into the medium follow the normal secretory route and that some of their oligosaccharides are subject to modifications known to affect many secretory glycoproteins during their passage through the Golgi apparatus. 相似文献
4.
Premature expression of cyclin B sensitizes human HT1080 cells to caffeine-induced premature mitosis
Eukaryotic cells do not normally initiate mitosis when DNA replication is blocked. This cell cycle checkpoint can be bypassed in some cells, however, by treatment with caffeine and certain other chemicals. Although S-phase arrested hamster cells undergo mitosis-specific events such as premature chromosome condensation (PCC) and nuclear envelope disassembly when exposed to caffeine, human cells show little response under the same conditions. To further investigate the molecular basis of this cell type specificity, a panel of hamster/human whole cell hybrids was created. The frequency of caffeine-induced PCC and the level of cyclin B-associated H1 kinase activity in the various hybrids were directly correlated with the extent of cyclin B synthesis during S-phase arrest. To determine whether expression of cyclin B alone could sensitize human cells to caffeine, cyclin B1 was transiently overexpressed in S-phase arrested HT1080 cells. The transfected cell population displayed a 5-fold increase in the frequency of caffeine-induced PCC when compared with normal HT1080 cells, roughly equivalent to the frequency of cells expressing exogenous epitope-tagged cyclin B1. In addition, immunofluorescent microscopy showed that individual cells overexpressing cyclin B1 during S phase arrest underwent PCC when exposed to caffeine. These results provide direct evidence that premature expression of cyclin B1 can make cells more vulnerable to chemically-induced uncoupling of mitosis from the completion of DNA replication. © 1995 Wiley-Liss, Inc. 相似文献
5.
Guo Y Kotova E Chen ZS Lee K Hopper-Borge E Belinsky MG Kruh GD 《The Journal of biological chemistry》2003,278(32):29509-29514
MRP8 (ABCC11) is a recently identified cDNA that has been assigned to the multidrug resistance-associated protein (MRP) family of ATP-binding cassette transporters, but its functional characteristics have not been determined. Here we examine the functional properties of the protein using transfected LLC-PK1 cells. It is shown that ectopic expression of MRP8 reduces basal intracellular levels of cAMP and cGMP and enhances cellular extrusion of cyclic nucleotides in the presence or absence of stimulation with forskolin or SIN-1A. Analysis of the sensitivity of MRP8-overexpressing cells revealed that they are resistant to a range of clinically relevant nucleotide analogs, including the anticancer fluoropyrimidines 5'-fluorouracil (approximately 3-fold), 5'-fluoro-2'-deoxyuridine (approximately 5-fold), and 5'-fluoro-5'-deoxyuridine (approximately 3-fold), the anti-human immunodeficiency virus agent 2',3'-dideoxycytidine (approximately 6-fold) and the anti-hepatitis B agent 9'-(2'-phosphonylmethoxynyl)adenine (PMEA) (approximately 5-fold). By contrast, increased resistance was not observed for several natural product chemotherapeutic agents. In accord with the notion that MRP8 functions as a drug efflux pump for nucleotide analogs, MRP8-transfected cells exhibited reduced accumulation and increased efflux of radiolabeled PMEA. In addition, it is shown by the use of in vitro transport assays that MRP8 is able to confer resistance to fluoropyrimidines by mediating the MgATP-dependent transport of 5'-fluoro-2'-deoxyuridine monophosphate, the cytotoxic intracellular metabolite of this class of agents, but not of 5'-fluorouracil or 5'-fluoro-2'-deoxyuridine. We conclude that MRP8 is an amphipathic anion transporter that is able to efflux cAMP and cGMP and to function as a resistance factor for commonly employed purine and pyrimidine nucleotide analogs. 相似文献
6.
Phylogenetic relationships were determined for 76 partial P-element
sequences from 14 species of the melanogaster species group within the
Drosophila subgenus Sophophora. These results are examined in the context
of the phylogeny of the species from which the sequences were isolated.
Sequences from the P-element family fall into distinct subfamilies, or
clades, which are often characteristic for particular species subgroups.
When examined locally among closely related species, the evolution of P
elements is characterized by vertical transmission, whereby the P-element
phylogeny traces the species phylogeny. On a broader scale, however, the
P-element phylogeny is not congruent with the species phylogeny. One
feature of P-element evolution in the melanogaster group is the presence of
more than one P-element subfamily, differing by as much as 36%, in the
genomes of some species. Thus, P elements from several individual species
are not monophyletic, and a likely explanation for the incongruence between
P-element and species phylogenies is provided by the comparison of
paralogous sequences. In certain instances, horizontal transfer seems to be
a valid alternative explanation for lack of congruence between species and
P-element phylogenies. The canonical P-element subfamily, which represents
the active, autonomous transposable element, is restricted to D.
melanogaster. Thus, its origin clearly lies outside of the melanogaster
species group, consistent with the earlier conclusion of recent horizontal
transfer.
相似文献
7.
Jose MG Vilar 《BMC systems biology》2010,4(1):152
Background
Cellular responses to death-promoting stimuli typically proceed through a differentiated multistage process, involving a lag phase, extensive death, and potential adaptation. Deregulation of this chain of events is at the root of many diseases. Improper adaptation is particularly important because it allows cell sub-populations to survive even in the continuous presence of death conditions, which results, among others, in the eventual failure of many targeted anticancer therapies. 相似文献8.
Lyon CM Klinge DM Liechty KC Gentry FD March TH Kang T Gilliland FD Adamova G Rusinova G Telnov V Belinsky SA 《Radiation research》2007,168(4):409-414
Epigenetic inactivation of genes by promoter hypermethylation, a major mechanism in the initiation and progression of tobacco-induced cancer, has also been associated with lung cancer induced through environmental and occupational exposures. Our previous study of gene methylation in workers from the MAYAK nuclear enterprise identified a significantly higher prevalence for methylation of the p16 gene (CDKN2A) in adenocarcinomas from workers compared to tumors from non-worker controls. The purpose of this investigation was to determine whether genes in addition to p16 are "targeted" for silencing and whether overall gene methylation was more common in radiation-induced adenocarcinoma. A significant increase in the prevalence of methylation of GATA5 was seen in tumors from workers compared to tumors from controls. The prevalence for methylation of PAX5 beta and H-cadherin did not differ in tumors from workers and controls. Evaluating the frequency for methylation of a five-gene panel revealed that 93% of adenocarcinomas from workers compared to 66% of tumors from controls were methylated for at least one gene. Moreover, a twofold increase was seen in the number of tumors methylated for three or more genes for tumors from workers compared to controls. Increased frequency for inactivation of genes by promoter hypermethylation and targeting of tumor suppressor genes such as GATA5 may be factors that contribute to the increased risk for lung cancer associated with radiation exposure. 相似文献
9.
10.
Alessandro S Guimarães Filipe B Carmo Marcos B Heinemann Ricardo WD Portela Roberto Meyer Andrey P Lage Núbia Seyffert Anderson Miyoshi Vasco Azevedo Aurora MG Gouveia 《BMC veterinary research》2011,7(1):1-5