首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   75篇
  免费   6篇
  2023年   2篇
  2021年   1篇
  2020年   2篇
  2019年   2篇
  2018年   3篇
  2017年   3篇
  2016年   2篇
  2015年   6篇
  2014年   7篇
  2013年   7篇
  2012年   7篇
  2011年   14篇
  2010年   6篇
  2009年   3篇
  2008年   6篇
  2007年   1篇
  2006年   3篇
  2005年   1篇
  2004年   3篇
  2003年   2篇
排序方式: 共有81条查询结果,搜索用时 15 毫秒
1.
Grooming in primates is often considered a “currency” that can be exchanged for other “services” or “commodities” such as reciprocal grooming, coalitionary support, infant handling, tolerance around food sources, active food sharing, or mating opportunities. Previous studies on primate grooming‐for‐sex exchange viewed the males as the demanding class, with the females as suppliers of mating opportunities. In this study, we examine the broader context of grooming‐for‐mating exchange in Barbary macaques in Gibraltar. Our data show that Barbary macaque males groom females with whom they are mating more frequently and for longer periods than other females, and the relationship between grooming and mating remains significant in both sexual and nonsexual contexts. In addition, females groomed males with whom they were mating more frequently and for longer periods than other males. In both sexes, grooming was observed to be far more frequent and to occur for longer durations in sexual compared to nonsexual contexts. We did not find any difference in grooming behavior between presexual and postsexual contexts. Our data suggest that there is no simple model to describe Barbary macaque grooming patterns in sexual contexts. Although our results are partly consistent with male use of grooming as payment for mating, broadly assessed grooming‐mating patterns cannot be solely explained by a male‐driven grooming‐for‐mating exchange.  相似文献   
2.
3.
As we have shown previously, yeast Mmi1 protein translocates from the cytoplasm to the outer surface of mitochondria when vegetatively growing yeast cells are exposed to oxidative stress. Here we analyzed the effect of heat stress on Mmi1 distribution. We performed domain analyses and found that binding of Mmi1 to mitochondria is mediated by its central alpha-helical domain (V-domain) under all conditions tested. In contrast, the isolated N-terminal flexible loop domain of the protein always displays nuclear localization. Using immunoelectron microscopy we confirmed re-location of Mmi1 to the nucleus and showed association of Mmi1 with intact and heat shock-altered mitochondria. We also show here that mmi1Δ mutant strains are resistant to robust heat shock with respect to clonogenicity of the cells. To elucidate this phenotype we found that the cytosolic Mmi1 holoprotein re-localized to the nucleus even in cells heat-shocked at 40°C. Upon robust heat shock at 46°C, Mmi1 partly co-localized with the proteasome marker Rpn1 in the nuclear region as well as with the cytoplasmic stress granules defined by Rpg1 (eIF3a). We co-localized Mmi1 also with Bre5, Ubp3 and Cdc48 which are involved in the protein de-ubiquitination machinery, protecting protein substrates from proteasomal degradation. A comparison of proteolytic activities of wild type and mmi1Δ cells revealed that Mmi1 appears to be an inhibitor of the proteasome. We conclude that one of the physiological functions of the multifunctional protein module, Mmi1, is likely in regulating degradation and/or protection of proteins thereby indirectly regulating the pathways leading to cell death in stressed cells.  相似文献   
4.
Abstract

The series of symmetrical and unsymmetrical isoquinolinium-5-carbaldoximes was designed and prepared for cholinesterase reactivation purposes. The novel compounds were evaluated for intrinsic acetylcholinesterase (AChE) or butyrylcholinesterase (BChE) inhibition, when the majority of novel compounds resulted with high inhibition of both enzymes and only weak inhibitors were selected for reactivation experiments on human AChE or BChE inhibited by sarin, VX, or paraoxon. The AChE reactivation for all used organophosphates was found negligible if compared to the reactivation ability of obidoxime. Importantly, two compounds were found to reactivate BChE inhibited by sarin or VX better to obidoxime at human attainable concentration. One compound resulted as better reactivator of NEMP (VX surrogate)-inhibited BChE than obidoxime. The in vitro results were further rationalized by molecular docking studies showing future directions on designing potent BChE reactivators.  相似文献   
5.
Regulation of gene expression on the level of translation and mRNA turnover is widely conserved evolutionarily. We have found that the main mRNA decay enzyme, exoribonuclease Xrn1, accumulates at the plasma membrane-associated eisosomes after glucose exhaustion in a culture of the yeast S. cerevisiae. Eisosomal localization of Xrn1 is not achieved in cells lacking the main component of eisosomes, Pil1, or Sur7, the protein accumulating at the membrane compartment of Can1 (MCC) - the eisosome-organized plasma membrane microdomain. In contrast to the conditions of diauxic shift, when Xrn1 accumulates in processing bodies (P-bodies), or acute heat stress, in which these cytosolic accumulations of Xrn1 associate with eIF3a/Rpg1-containing stress granules, Xrn1 is not accompanied by other mRNA-decay machinery components when it accumulates at eisosomes in post-diauxic cells. It is important that Xrn1 is released from eisosomes after addition of fermentable substrate. We suggest that this spatial segregation of Xrn1 from the rest of the mRNA-decay machinery reflects a general regulatory mechanism, in which the key enzyme is kept separate from the rest of mRNA decay factors in resting cells but ready for immediate use when fermentable nutrients emerge and appropriate metabolism reprogramming is required. In particular, the localization of Xrn1 to the eisosome, together with previously published data, accents the relevance of this plasma membrane-associated compartment as a multipotent regulatory site.  相似文献   
6.
The Cdk12/CycK complex promotes expression of a subset of RNA polymerase II genes, including those of the DNA damage response. CDK12 is among only nine genes with recurrent somatic mutations in high-grade serous ovarian carcinoma. However, the influence of these mutations on the Cdk12/CycK complex and their link to cancerogenesis remain ill-defined. Here, we show that most mutations prevent formation of the Cdk12/CycK complex, rendering the kinase inactive. By examining the mutations within the Cdk12/CycK structure, we find that they likely provoke structural rearrangements detrimental to Cdk12 activation. Our mRNA expression analysis of the patient samples containing the CDK12 mutations reveals coordinated downregulation of genes critical to the homologous recombination DNA repair pathway. Moreover, we establish that the Cdk12/CycK complex occupies these genes and promotes phosphorylation of RNA polymerase II at Ser2. Accordingly, we demonstrate that the mutant Cdk12 proteins fail to stimulate the faithful DNA double strand break repair via homologous recombination. Together, we provide the molecular basis of how mutated CDK12 ceases to function in ovarian carcinoma. We propose that CDK12 is a tumor suppressor of which the loss-of-function mutations may elicit defects in multiple DNA repair pathways, leading to genomic instability underlying the genesis of the cancer.  相似文献   
7.

Introduction

Cannabis is Europe''s most commonly used illicit drug. Some users do not develop dependence or other problems, whereas others do. Many factors are associated with the occurrence of cannabis-related disorders. This makes it difficult to identify key risk factors and markers to profile at-risk cannabis users using traditional hypothesis-driven approaches. Therefore, the use of a data-mining technique called binary recursive partitioning is demonstrated in this study by creating a classification tree to profile at-risk users.

Methods

59 variables on cannabis use and drug market experiences were extracted from an internet-based survey dataset collected in four European countries (Czech Republic, Italy, Netherlands and Sweden), n = 2617. These 59 potential predictors of problematic cannabis use were used to partition individual respondents into subgroups with low and high risk of having a cannabis use disorder, based on their responses on the Cannabis Abuse Screening Test. Both a generic model for the four countries combined and four country-specific models were constructed.

Results

Of the 59 variables included in the first analysis step, only three variables were required to construct a generic partitioning model to classify high risk cannabis users with 65–73% accuracy. Based on the generic model for the four countries combined, the highest risk for cannabis use disorder is seen in participants reporting a cannabis use on more than 200 days in the last 12 months. In comparison to the generic model, the country-specific models led to modest, non-significant improvements in classification accuracy, with an exception for Italy (p = 0.01).

Conclusion

Using recursive partitioning, it is feasible to construct classification trees based on only a few variables with acceptable performance to classify cannabis users into groups with low or high risk of meeting criteria for cannabis use disorder. The number of cannabis use days in the last 12 months is the most relevant variable. The identified variables may be considered for use in future screeners for cannabis use disorders.  相似文献   
8.
HIC1 (hypermethylated in cancer 1) is a tumor suppressor gene located on chromosome 17p13.3, a region frequently hypermethylated or deleted in human neoplasias. In mouse, Hic1 is essential for embryonic development and exerts an antitumor role in adult animals. Since Hic1-deficient mice die perinatally, we generated a conditional Hic1 null allele by flanking the Hic1-coding region by loxP sites. When crossed to animals expressing Cre recombinase in a cell-specific manner, the Hic1 conditional mice will provide new insights into the function of Hic1 in developing and mature tissues. Additionally, we used gene targeting to replace sequence-encoding amino acids 186-893 of Hic1 by citrine fluorescent protein cDNA. We demonstrate that the distribution of Hic1-citrine fusion polypeptide corresponds to the expression pattern of wild-type Hic1. Consequently, Hic1-citrine "reporter" mice can be used to monitor the activity of the Hic1 locus using citrine fluorescence.  相似文献   
9.
10.
The family Cobitidae represents a characteristic element of the Eurasian ichthyofauna. Despite diverse features of sexual dimorphism, comparably few morphological characters have been utilized for taxonomic studies resulting in many unresolved puzzles. Here we present the phylogenetic relationships of Cobitidae as inferred from the mitochondrial cytochrome b gene and the nuclear gene RAG-1. Analyses of both markers show a group of eight nominal genera, which all occur in Europe and eastern, northern and western Asia, forming a monophyletic lineage (northern clade) while all other clades inhabit South and Southeast Asia (southern lineages). While all eight southern lineages correspond to genera as defined by morphological studies, only four lineages were reliably recovered within the northern clade, and of these only one (Sabanejewia) corresponds to a formerly considered genus. The genera Cobitis, Iksookimia and Niwa?lla were polyphyletic. A comparison of the two markers shows several incongruities within the northern clade and mitochondrial introgression at least in the genus Misgurnus. Mapping the characters of sexual dimorphism on our cladogram, we identified five character states that are diagnostic for certain lineages. Estimations of the divergence times dated the separation of the northern clade from the southern lineages to the middle Eocene (46 MYA) and the origin of "Cobitis"misgurnoides, the basal taxon of the northern clade, during early Oligocene (30-35 MYA). The geographic distribution of the major clades supports recently developed hypotheses about the river history of East Asia and further suggests that a range expansion of the northern clade in late Miocene (15 MYA) led to the colonisation of Europe by three already distinct genera.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号