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101.
Annike Rand Meike Stiesch Michael Eisenburger 《Computer methods in biomechanics and biomedical engineering》2017,20(10):1132-1139
In almost all finite element (FE) studies in dentistry, virtual forces are applied directly to dentures. The purpose of this study was to develop a FE model with non-linear contact simulation using an antagonist as force transmitter and to compare this with a similar model that uses direct force transmission. Furthermore, five contact situations were created in order to examine their influence on the peri-implant bone stresses, which are relevant to the survival rate of implants. It was found that the peri-implant bone stresses were strongly influenced by the kind of force transmission and contact number. 相似文献
102.
103.
Rand DM 《Genetica》2011,139(5):685-697
Biological variation exists across a nested set of hierarchical levels from nucleotides within genes to populations within
species to lineages within the tree of life. How selection acts across this hierarchy is a long-standing question in evolutionary
biology. Recent studies have suggested that genome size is influenced largely by the balance of selection, mutation and drift
in lineages with different population sizes. Here we use population cage and maternal transmission experiments to identify
the relative strength of selection at an individual and cytoplasmic level. No significant trends were observed in the frequency
of large (L) and small (S) mtDNAs across 14 generations in population cages. In all replicate cages, new length variants were
observed in heteroplasmic states indicating that spontaneous length mutations occurred in these experimental populations.
Heteroplasmic flies carrying L genomes were more frequent than those carrying S genomes suggesting an asymmetric mutation
dynamic from larger to smaller mtDNAs. Mother-offspring transmission of heteroplasmy showed that the L mtDNA increased in
frequency within flies both between and within generations despite sampling drift of the same intensity as occurred in population
cages. These results suggest that selection for mtDNA size is stronger at the cytoplasmic than at the organismal level. The
fixation of novel mtDNAs within and between species requires a transient intracellular heteroplasmic stage. The balance of
population genetic forces at the cytoplasmic and individual levels governs the units of selection on mtDNA, and has implications
for evolutionary inference as well as for the effects of mtDNA mutations on fitness, disease and aging. 相似文献
104.
Dan E. Wells Laura Gutierrez Zhenkang Xu Vladimir Krylov Jaroslav Macha Kerstin P. Blankenburg Matthew Hitchens Larry J. Bellot Mary Spivey Derek L. Stemple Andria Kowis Yuan Ye Shiran Pasternak Jenetta Owen Thu Tran Renata Slavikova Lucie Tumova Tereza Tlapakova Eva Seifertova Steven E. Scherer Amy K. Sater 《Developmental biology》2011,(1):507
We present a genetic map for Xenopus tropicalis, consisting of 2886 Simple Sequence Length Polymorphism (SSLP) markers. Using a bioinformatics-based strategy, we identified unique SSLPs within the X. tropicalis genome. Scaffolds from X. tropicalis genome assembly 2.0 (JGI) were scanned for Simple Sequence Repeats (SSRs); unique SSRs were then tested for amplification and polymorphisms using DNA from inbred Nigerian and Ivory Coast individuals. Thus identified, the SSLPs were genotyped against a mapping cross panel of DNA samples from 190 F2 individuals. Nearly 4000 SSLPs were genotyped, yielding a 2886-marker genetic map consisting of 10 major linkage groups between 73 and 132 cM in length, and 4 smaller linkage groups between 7 and 40 cM. The total effective size of the map is 1658 cM, and the average intermarker distance for each linkage group ranged from 0.27 to 0.75 cM. Fluorescence In Situ Hybridization (FISH) was carried out using probes for genes located on mapped scaffolds to assign linkage groups to chromosomes. Comparisons of this map with the X. tropicalis genome Assembly 4.1 (JGI) indicate that the map provides representation of a minimum of 66% of the X. tropicalis genome, incorporating 758 of the approximately 1300 scaffolds over 100,000 bp. The genetic map and SSLP marker database constitute an essential resource for genetic and genomic analyses in X. tropicalis. 相似文献
105.
Ulfert Rand Upneet Hillebrand Stephanie Sievers Steffi Willenberg Mario K?ster Hansj?rg Hauser Dagmar Wirth 《Nucleic acids research》2014,42(13):e109
Antiviral defence in mammals is mediated through type-I interferons (IFNs). Viruses antagonise this process through expression of IFN antagonist proteins (IAPs). Understanding and modelling of viral escape mechanisms and the dynamics of IAP action has the potential to facilitate the development of specific and safe drugs. Here, we describe the dynamics of interference by selected viral IAPs, NS1 from Influenza A virus and NS3/4A from Hepatitis C virus. We used Tet-inducible IAP gene expression to uncouple this process from virus-driven dynamics. Stochastic activation of the IFN-β gene required the use of single-cell live imaging to define the efficacy of the inhibitors during the virus-induced signalling processes. We found significant correlation between the onset of IAP expression and halted IFN-β expression in cells where IFN-β induction had already occurred. These data indicate that IAPs not only prevent antiviral signalling prior to IFN-β induction, but can also stop the antiviral response even after it has been activated. We found reduced NF-κB activation to be the underlying mechanism by which activated IFN expression can be blocked. This work demonstrates a new mechanism by which viruses can antagonise the IFN response. 相似文献
106.
107.
What makes people willing to pay costs to benefit others? Does such cooperation require effortful self-control, or do automatic, intuitive processes favor cooperation? Time pressure has been shown to increase cooperative behavior in Public Goods Games, implying a predisposition towards cooperation. Consistent with the hypothesis that this predisposition results from the fact that cooperation is typically advantageous outside the lab, it has further been shown that the time pressure effect is undermined by prior experience playing lab games (where selfishness is the more advantageous strategy). Furthermore, a recent study found that time pressure increases cooperation even in a game framed as a competition, suggesting that the time pressure effect is not the result of social norm compliance. Here, we successfully replicate these findings, again observing a positive effect of time pressure on cooperation in a competitively framed game, but not when using the standard cooperative framing. These results suggest that participants'' intuitions favor cooperation rather than norm compliance, and also that simply changing the framing of the Public Goods Game is enough to make it appear novel to participants and thus to restore the time pressure effect. 相似文献
108.
Seed dispersal, habitat suitability and the distribution of halophytes across a salt marsh tidal gradient 总被引:15,自引:4,他引:11
Tatyana A. Rand 《Journal of Ecology》2000,88(4):608-621
109.
The bacteriophage T4 gene for the small subunit of ribonucleotide reductase contains an intron. 总被引:21,自引:3,他引:21
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The bacteriophage T4 gene nrdB codes for the small subunit of the enzyme ribonucleotide reductase. The T4 nrdB gene was localized between 136.1 kb and 137.8 kb in the T4 genetic map according to the deduced structural homology of the protein to the amino acid sequence of its bacterial counterpart, the B2 subunit of Escherichia coli. This positions the C-terminal end of the T4 nrdB gene approximately 2 kb closer to the T4 gene 63 than earlier anticipated from genetic recombinational analyses. The most surprising feature of the T4 nrdB gene is the presence of an approximately 625 bp intron which divides the structural gene into two parts. This is the second example of a prokaryotic structural gene with an intron. The first prokaryotic intron was reported in the nearby td gene, coding for the bacteriophage T4-specific thymidylate synthase enzyme. The nucleotide sequence at the exon-intron junctions of the T4 nrdB gene is similar to that of the junctions of the T4 td gene: the anticipated exon-intron boundary at the donor site ends with a TAA stop codon and there is an ATG start codon at the putative downstream intron-exon boundary of the acceptor site. In the course of this work the denA gene of T4 (endonuclease II) was also located. 相似文献
110.
The acetylcholinesterase genes of C. elegans: identification of a third gene (ace-3) and mosaic mapping of a synthetic lethal phenotype 总被引:7,自引:0,他引:7
In C. elegans, the newly identified ace-3 is the third gene affecting acetylcholinesterase (AChE) activity. ace-3 II specifically affects class C AChE and is unlinked to ace-1 X or ace-2 I, which affect the other two AChE classes (A and B, respectively). Strains homozygous for an ace-3 mutation have no apparent behavioral or developmental defect; ace-1 ace-3 and ace-2 ace-3 double mutants are also nearly wild type. In contrast, ace-1 ace-2 ace-3 triple mutant animals are paralyzed and developmentally arrested; their embryonic development is relatively unimpaired, but they are unable to grow beyond the hatching stage. Based on the analysis of genetic mosaics, we conclude that in the absence of ace-2 and ace-3 function, the expression of ace-1(+) in muscle cells, but not in neurons, is essential for postembryonic viability. 相似文献