排序方式: 共有23条查询结果,搜索用时 15 毫秒
11.
12.
BACKGROUND: Insect symbionts employ multiple strategies to enhance their spread through populations, and some play a dual role as both a mutualist and a reproductive manipulator. It has recently been found that this is the case for some strains of Wolbachia, which both cause cytoplasmic incompatibility and protect their hosts against viruses. Here, we carry out the first test as to whether a male-killing strain of Wolbachia also provides a direct benefit to its host by providing antiviral protection to its host Drosophila bifasciata. We infected flies with two positive sense RNA viruses known to replicate in a range of Drosophila species (Drosophila C virus and Flock House virus) and measure the rate of death in Wolbachia positive and negative host lines with the same genetic background. RESULTS: Both viruses caused considerable mortality to D. bifasciata flies, with Drosophila C virus killing 43% more flies than the uninfected controls and Flock House virus killing 78% more flies than the uninfected controls. However, viral induced mortality was unaffected by the presence of Wolbachia. CONCLUSION: In the first male-killing Wolbachia strain tested for antiviral effects, we found no evidence that it conferred protection against two RNA viruses. We show that although antiviral resistance is widespread across the Wolbachia phylogeny, the trait seems to have been lost or gained along some lineages. We discuss the potential mechanisms of this, and can seemingly discount protection against these viruses as a reason why this symbiont has spread through Drosophila populations. 相似文献
13.
Background
Microsatellites (or short tandem repeats, STRs) are the genetic markers of choice for studying Aspergillus fumigatus molecular epidemiology due to its reproducibility and high discrimination power. However, the specificity of these markers must be investigated in a group of isolates from closely related species. The aim of this work was to test a microsatellite-based PCR multiplex previously designed for A. fumigatus in a set of species belonging to section Fumigati, namely Aspergillus fumigatiaffinis, Aspergillus lentulus, Aspergillus novofumigatus, Aspergillus unilateralis, Aspergillus viridinutans, Neosartorya fischeri, Neosartorya hiratsukae, Neosartorya pseudofischeri and Neosartorya udagawae.Results
The reference A. fumigatus strain ATCC 46645 was easily genotyped in standard conditions showing a final electrophoretic profile of 8 expected peaks corresponding to each microsatellite locus. Inversely, no peaks were observed for all other species from section Fumigati, with an exception for marker MC6b in A. unilateralis. By screening the genome sequence of Neosartorya fischeri NRRL 181, the results showed that MC3, MC6a and MC7 might be employed for N. fischeri genotyping since these markers present several repeats of each motif. The accumulation of insertions and deletions was frequently observed in the genomic regions surrounding the microsatellites, including those where the A. fumigatus primers are located. The amplification of microsatellite markers in less stringent amplification conditions resulted in a distinct electrophoretic profile for species within section Fumigati.Conclusions
Therefore, the microsatellite-based PCR multiplex allow simple identification of A. fumigatus and, with a slight modification of temperature conditions, it also allows discriminating other pathogenic species within section Fumigati, particularly A. fumigatiaffinis, N. fischeri and N. udagawae. 相似文献14.
Ribosomal protein S14 genes (RPS14) in eukaryotic species from protozoa to
primates exhibit dramatically different intron-exon structures yet share
homologous polypeptide-coding sequences. To recognize common features of
RPS14 gene architectures in closely related mammalian species and to
evaluate similarities in their noncoding DNA sequences, we isolated the
intron-containing S14 locus from Chinese hamster ovary (CHO) cell DNA by
using a PCR strategy and compared it with human RPS14. We found that rodent
and primate S14 genes are composed of identical protein-coding exons
interrupted by introns at four conserved DNA sites. However, the structures
of corresponding CHO and human RPS14 introns differ significantly.
Nonetheless, individual intron splice donor, splice acceptor, and upstream
flanking motifs have been conserved within mammalian S14 homologues as well
as within RPS14 gene fragments PCR amplified from other vertebrate genera
(birds and bony fish). Our data indicate that noncoding, intronic DNA
sequences within highly conserved, single-copy ribosomal protein genes are
useful molecular landmarks for phylogenetic analysis of closely related
vertebrate species.
相似文献
15.
AE Clarke S Bernatsky KH Costenbader MB Urowitz DD Gladman PR Fortin M Petri S Manzi DA Isenberg A Rahman D Wallace C Gordon C Peschken MA Dooley EM Ginzler C Aranow SM Edworthy O Nived S Jacobsen G Ruiz-Irastorza E Yelin SG Barr L Criswell G Sturfelt L Dreyer I Blanco L Gottesman CH Feldman R Ramsey-Goldman 《Arthritis research & therapy》2012,14(Z3):A16
16.
Background
Selfish genetic elements that distort the sex ratio are found widely. Notwithstanding the number of records of sex ratio distorters, their incidence is poorly understood. Two factors can prevent a sex ratio distorter from invading: inability of the sex ratio distorter to function (failure of mechanism or transmission), and lack of drive if they do function (inappropriate ecology for invasion). There has been no test to date on factors causing variation in the incidence of sex ratio distorting cytoplasmic bacteria. We therefore examined whether absence of the male-killing Wolbachia infection in D. bifasciata in Hokkaido island of Japan, in contrast to the presence of infection on the proximal island of Honshu, was associated with failure of the infection to function properly on the Hokkaido genetic background. 相似文献17.
Participation of plasma membrane proteins in the formation of tight junction by cultured epithelial cells
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)
Measurements of the transepithelial electrical resistance correlated with freeze-fracture observations have been used to study the process of tight junction formation under various experimental conditions in monolayers of the canine kidney epithelial cell line MDCK. Cells derived from previously confluent cultures and plated immediately after trypsin- EDTA dissociation develop a resistance that reaches its maximum value of several hundred ohms-cm(2) after approximately 24 h and falls to a steady-state value of 80-150 ohms- cm(2) by 48 h. The rise in resistance and the development of tight junctions can be completely and reversibly prevented by the addition of 10 μg/ml cycloheximide at the time of plating, but not when this inhibitor is added more than 10 h after planting. Thus tight junction formation consists of separable synthetic and assembly phases. These two phases can also be dissociated and the requirement for protein synthesis after plating eliminated if, following trypsinization, the cells are maintained in spinner culture for 24 h before plating. The requirement for protein synthesis is restored, however, if cells maintained in spinner culture are treated with trypsin before plating. Actinomycin D prevents development of resistance only in monolayers formed from cells derived from sparse rather than confluent cultures, but new mRNA synthesis is not required if cells obtained from sparse cultures are maintained for 24 h in spinner culture before plating. Once a steady-state resistance has been reached, its maintenance does not require either mRNA or protein synthesis; in fact, inhibition of protein synthesis causes a rise in the resistance over a 30-h period. Following treatments that disrupt the junctions in steady- state monolayers recovery of resistance also does not require protein synthesis. These observations suggest that proteins are involved in tight junction formation. Such proteins, which do not turn over rapidly under steady-state conditions, are destroyed by trypsinization and can be resynthesized in the absence of stable cell-cell or cell-substratum contact. Messenger RNA coding for proteins involved in tight junction formation is stable except when cells are sparsely plated, and can also be synthesized without intercellular contacts or cell-substratum attachment. 相似文献
18.
A comparison of two methods for constructing evolutionary distances from a weighted contribution of transition and transversion differences 总被引:3,自引:3,他引:0
Since the initial work of Jukes and Cantor (1969), a number of procedures
have been developed to estimate the expected number of nucleotide
substitutions corresponding to a given observed level of nucleotide
differentiation assuming particular evolutionary models. Unlike the
proportion of different sites, the expected number of substitutions that
would have occurred grows linearly with time and therefore has had great
appeal as an evolutionary distance. Recently, however, a number of authors
have tried to develop improved statistical approaches for generating and
evaluating evolutionary distances (Schoniger and von Haeseler 1993;
Goldstein and Polock 1994; Tajima and Takezaki 1994). These studies clearly
show that the estimated number of nucleotide substitutions is generally not
the best estimator for use in reconstruction of phylogenetic relationships.
The reason for this is that there is often a large error associated with
the estimation of this number. Therefore, even though its expectation is
correct (i.e., on average the expected number of substitutions is
proportional to time- -but see Tajima 1993), it is not expected to be as
useful as estimators designed to have a lower variance.
相似文献
19.
WJ Richardson DD van der Voort E Wilson JE Moore Jr. 《Molecular & cellular biomechanics : MCB》2013,10(3):245-265
Non-uniform stress and strain fields are prevalent in many tissues in vivo, and often exacerbated by disease or injury. These mechanical gradients potentially play a role in contributing to pathological conditions, presenting a need for experimental tools to allow investigation of cell behavior within non-uniformly stimulated environments. Herein, we employ two in vitro cell-stretching devices (one previously published; one newly presented) capable of subjecting cells to cyclic, non-uniform stretches upon the surface of either a circular elastomeric membrane or a cylindrical PDMS tube. After 24 hours of cyclic stretch, 10T1/2 cells on both devices showed marked changes in long-axis orientation, with tendencies to align parallel to the direction of minimal deformation. The degree of this response varied depending on location within the stretch gradients. These results demonstrated the feasibility of conducting cell mechanobiology investigations with the two novel devices, while also highlighting the experimental capabilities of non-uniform mechanical environments for these types of studies. Such capabilities include robust data collection for developing mechanobiological dose-response curves, signal threshold identification, and potential spatial targeting for drug delivery. 相似文献
20.