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排序方式: 共有302条查询结果,搜索用时 31 毫秒
1.
Francisco Barja Marie-Louise Chappuis Gilbert Turian 《FEMS microbiology letters》1993,107(2-3):261-266
Abstract Anti-actin drugs, cytochalasins A and B, inhibited both normal single, and benomyl-induced multiple, germ tube outgrowth from conidia of Neurospora crassa . Actin was cytochemically found to be concentrated in each of the benomyl-induced germ tube tips. No significant quantitative changes either in total actin or its isoforms were measured in the inhibitor-treated germlings. While intact microtubules are required for normal, monopolar axiation of the germ tube, they appear not to be necessary for benomyl-induced multipolar outgrowth which, in contrast, still requires intact actin microfilaments. Microfilaments and microtubules thus play complementary roles in the normal germination of conidia. 相似文献
2.
Using the imidate procedure, 2,3,4,6-tetra-O-benzyl-1-O-(N-methylacetimidoyl)-β-d-galactopyranose was condensed with various monosaccharides to provide, in good yield and with high stereoselectivity, α-linked disaccharides. 相似文献
3.
Emily A. Sloan Mary F. Kearney Laurie R. Gray Kathryn Anastos Eric S. Daar Joseph Margolick Frank Maldarelli Marie-Louise Hammarskjold David Rekosh 《Journal of virology》2013,87(20):11173-11186
HIV-1 Rev and the Rev response element (RRE) enable a critical step in the viral replication cycle by facilitating the nuclear export of intron-containing mRNAs, yet their activities have rarely been analyzed in natural infections. This study characterized their genetic and functional variation in a small cohort of HIV-infected individuals. Multiple Rev and RRE sequences were obtained using single-genome sequencing (SGS) of plasma samples collected within 6 months after seroconversion and at a later time. This allowed the identification of cognate sequences that were linked in vivo in the same viral genome and acted together as a functional unit. Phylogenetic analyses of these sequences indicated that 4/5 infections were founded by a single transmission event. Rev and RRE variants from each time point were subjected to functional analysis as both cognate pairs and as individual components. While a range of Rev-RRE activities were seen, the activity of cognate pairs from a single time point clustered to a discrete level, which was termed the set point. In 3/5 patients, this set point changed significantly over the time period studied. In all patients, RRE activity was more sensitive to sequence variation than Rev activity and acted as the primary driver of the cognate set point. Selected patient RREs were also shown to have differences in Rev multimerization using gel shift binding assays. Thus, rather than acting as a simple on-off switch or maintaining a constant level of activity throughout infection, the Rev-RRE system can fluctuate, presumably to control replication. 相似文献
4.
Chringma Sherpa Jason W. Rausch Stuart F.J. Le?Grice Marie-Louise Hammarskjold David Rekosh 《Nucleic acids research》2015,43(9):4676-4686
The HIV Rev protein forms a complex with a 351 nucleotide sequence present in unspliced and incompletely spliced human immunodeficiency virus (HIV) mRNAs, the Rev response element (RRE), to recruit the cellular nuclear export receptor Crm1 and Ran-GTP. This complex facilitates nucleo-cytoplasmic export of these mRNAs. The precise secondary structure of the HIV-1 RRE has been controversial, since studies have reported alternative structures comprising either four or five stem-loops. The published structures differ only in regions that lie outside of the primary Rev binding site. Using in-gel SHAPE, we have now determined that the wt NL4-3 RRE exists as a mixture of both structures. To assess functional differences between these RRE ‘conformers’, we created conformationally locked mutants by site-directed mutagenesis. Using subgenomic reporters, as well as HIV replication assays, we demonstrate that the five stem-loop form of the RRE promotes greater functional Rev/RRE activity compared to the four stem-loop counterpart. 相似文献
5.
Michael D. Moore Olga A. Nikolaitchik Jianbo Chen Marie-Louise Hammarskj?ld David Rekosh Wei-Shau Hu 《PLoS pathogens》2009,5(10)
Once transcribed, the nascent full-length RNA of HIV-1 must travel to the appropriate host cell sites to be translated or to find a partner RNA for copackaging to form newly generated viruses. In this report, we sought to delineate the location where HIV-1 RNA initiates dimerization and the influence of the RNA transport pathway used by the virus on downstream events essential to viral replication. Using a cell-fusion-dependent recombination assay, we demonstrate that the two RNAs destined for copackaging into the same virion select each other mostly within the cytoplasm. Moreover, by manipulating the RNA export element in the viral genome, we show that the export pathway taken is important for the ability of RNA molecules derived from two viruses to interact and be copackaged. These results further illustrate that at the point of dimerization the two main cellular export pathways are partially distinct. Lastly, by providing Gag in trans, we have demonstrated that Gag is able to package RNA from either export pathway, irrespective of the transport pathway used by the gag mRNA. These findings provide unique insights into the process of RNA export in general, and more specifically, of HIV-1 genomic RNA trafficking. 相似文献
6.
Jeffrey Q. Chambers Amanda L. Robertson Vilany M. C. Carneiro Adriano J. N. Lima Marie-Louise Smith Lucie C. Plourde Niro Higuchi 《Oecologia》2009,160(1):107-117
Advanced recruitment and neutral processes play important roles in determining tree species composition in tropical forest
canopy gaps, with few gaps experiencing clear secondary successional processes. However, most studies are limited to the relatively
limited spatial scales provided by forest inventory plots, and investigations over the entire range of gap size are needed
to better understand how ecological processes vary with tree mortality events. This study employed a landscape approach to
test the hypothesis that tree species composition and forest structural attributes differ between large blowdown gaps and
relatively undisturbed primary forest. Spectral mixture analysis on hyperspectral satellite imagery was employed to direct
field sampling to widely distributed sites, and blowdown plots were compared with undisturbed primary forest plots. Tree species
composition and forest structural attributes differed markedly between gap and non-gap sites, providing evidence of niche
partitioning in response to disturbance across the region. Large gaps were dominated by classic Neotropical pioneer genera
such as Cecropia and Vismia, and average tree size was significantly smaller. Mean wood density of trees recovering in large gaps (0.55 g cm−3) was significantly lower than in primary forest plots (0.71 g cm−3), a difference similar to that found when comparing less dynamic (i.e., tree recruitment, growth, and mortality) Central
Amazon forests with more dynamic Western Amazon forests. Based on results, we hypothesize that the importance of neutral processes
weaken, and niche processes strengthen, in determining community assembly along a gradient in gap size and tree mortality
intensity. Over evolutionary time scales, pervasive dispersal among colonizers could result in the loss of tree diversity
in the pioneer guild through competitive exclusion. Results also underscore the importance of considering disturbance processes
across the landscape when addressing forest carbon balance. 相似文献
7.
Cord Drögemüller Marco Rossi Arcangelo Gentile Stefania Testoni Hannes Jörg Gerald Stranzinger Michaela Drögemüller Marie-Louise Glowatzki-Mullis Tosso Leeb 《Mammalian genome》2009,20(1):53-59
Arachnomelia in Brown Swiss cattle is a monogenic autosomal recessive inherited congenital disorder of the skeletal system
giving affected calves a spidery look (OMIA ID 000059). Over a period of 20 years 15 cases were sampled in the Swiss and Italian
Brown cattle population. Pedigree data revealed that all affected individuals trace back to a single acknowledged carrier
founder sire. A genome scan using 240 microsatellites spanning the 29 bovine autosomes showed homozygosity at three adjacent
microsatellite markers on bovine Chr 5 in all cases. Linkage analysis confirmed the localization of the arachnomelia mutation
in the region of the marker ETH10. Fine-mapping and haplotype analysis using a total of 34 markers in this region refined the critical region of the arachnomelia
locus to a 7.19-Mb interval on bovine Chr 5. The disease-associated IBD haplotype was shared by 36 proven carrier animals
and allows marker-assisted selection. As the corresponding human and mouse chromosome segments do not contain any clear functional
candidate genes for this disorder, the mutation causing arachnomelia in the Brown Swiss cattle might help to identify an unknown
gene in bone development.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
8.
Andrew D. Foote Jason Newton María C. ávila-Arcos Marie-Louise Kampmann Jose A. Samaniego Klaas Post Aqqalu Rosing-Asvid Mikkel-Holger S. Sinding M. Thomas P. Gilbert 《Proceedings. Biological sciences / The Royal Society》2013,280(1768)
Niche variation owing to individual differences in ecology has been hypothesized to be an early stage of sympatric speciation. Yet to date, no study has tracked niche width over more than a few generations. In this study, we show the presence of isotopic niche variation over millennial timescales and investigate the evolutionary outcomes. Isotopic ratios were measured from tissue samples of sympatric killer whale Orcinus orca lineages from the North Sea, spanning over 10 000 years. Isotopic ratios spanned a range similar to the difference in isotopic values of two known prey items, herring Clupea harengus and harbour seal Phoca vitulina. Two proxies of the stage of speciation, lineage sorting of mitogenomes and genotypic clustering, were both weak to intermediate indicating that speciation has made little progress. Thus, our study confirms that even with the necessary ecological conditions, i.e. among-individual variation in ecology, it is difficult for sympatric speciation to progress in the face of gene flow. In contrast to some theoretical models, our empirical results suggest that sympatric speciation driven by among-individual differences in ecological niche is a slow process and may not reach completion. We argue that sympatric speciation is constrained in this system owing to the plastic nature of the behavioural traits under selection when hunting either mammals or fish. 相似文献
9.
Portia C. Mutevedzi Alison J. Rodger Paul Kowal Makandwe Nyirenda Marie-Louise Newell 《PloS one》2013,8(10)
Background
The association of HIV with chronic morbidity and inflammatory markers (cytokines) in older adults (50+years) is potentially relevant for clinical care, but data from African populations is scarce.Objective
To examine levels of chronic morbidity by HIV and ART status in older adults (50+years) and subsequent associations with selected pro-inflammatory cytokines and body mass index.Methods
Ordinary, ordered and generalized ordered logistic regression techniques were employed to compare chronic morbidity (heart disease (angina), arthritis, stroke, hypertension, asthma and diabetes) and cytokines (Interleukins-1 and -6, C-Reactive Protein and Tumor Necrosis Factor-alpha) by HIV and ART status on a cross-sectional random sample of 422 older adults nested within a defined rural South African population based demographic surveillance.Results
Using a composite measure of all morbidities, controlling for age, gender, BMI, smoking and wealth quintile, HIV-infected individuals on ART had 51% decreased odds (95% CI:0.26-0.92) of current morbidity compared to HIV-uninfected. In adjusted regression, compared to HIV-uninfected, the proportional odds (aPOR) of having elevated inflammation markers of IL6 (>1.56pg/mL) was nearly doubled in HIV-infected individuals on (aPOR 1.84; 95%CI: 1.05-3.21) and not on (aPOR 1.94; 95%CI: 1.11-3.41) ART. Compared to HIV-uninfected, HIV-infected individuals on ART had >twice partial proportional odds (apPOR=2.30;p=0.004) of having non-clinically significant raised hsCRP levels(>1ug/mL); ART-naïve HIV-infected individuals had >double apPOR of having hsCRP levels indicative of increased heart disease risk(>3.9ug/mL;p=0.008).Conclusions
Although HIV status was associated with increased inflammatory markers, our results highlight reduced morbidity in those receiving ART and underscore the need of pro-actively extending these services to HIV-uninfected older adults, beyond mere provision at fixed clinics. Providing health services through regular community chronic disease screening would ensure health care reaches all older adults in need. 相似文献10.
Permethylated C-glycosylflavones give well defined MS, including in all cases an important molecular peak. The observed fragmentations are characteristic for the nature and position of the sugar. The 6-C and 8-C glycosylated derivatives are clearly differentiated. In dissymmetrical 6,8-di-C-glycosylflavones, the natures of the sugar in both the 6- and 8- positions can be determined. The structures of several natural compounds are discussed. 相似文献