Search results for "replica"
showing 10 items of 576 documents
The cost of replication fidelity in human immunodeficiency virus type 1.
2006
Mutation rates should be governed by at least three evolutionary factors: the need for beneficial mutations, the benefit of minimizing the mutational load and the cost of replication fidelity. RNA viruses show high mutation rates compared with DNA micro-organisms, and recent findings suggest that the cost of fidelity might play a role in the evolution of increased mutation rates. Here, by analysing previously published data from HIV-1 reverse transcriptase in vitro assays, we show a trade-off between enzymatic accuracy and the maximum rate of polymerization, thus providing a biochemical basis for the fitness cost of fidelity in HIV-1. This trade-off seems to be related to inefficient exten…
Effect of Ribavirin on the Mutation Rate and Spectrum of Hepatitis C Virus In Vivo
2009
ABSTRACTTheir extremely error-prone replication makes RNA viruses targets for lethal mutagenesis. In the case of hepatitis C virus (HCV), the standard treatment includes ribavirin, a base analog with an in vitro mutagenic effect, but the in vivo mode of action of ribavirin remains poorly understood. Here, we test the mutagenic effects of ribavirin plus interferon treatment in vivo using a new method to estimate mutation rates based on the analysis of nonsense mutations. We apply this methodology to a large HCV sequence database containing over 15,000 reverse transcription-PCR molecular clone sequences from 74 patients infected with HCV. We obtained an estimate of the spontaneous mutation ra…
Variation in RNA virus mutation rates across host cells.
2014
It is well established that RNA viruses exhibit higher rates of spontaneous mutation than DNA viruses and microorganisms. However, their mutation rates vary amply, from 10−6 to 10−4 substitutions per nucleotide per round of copying (s/n/r) and the causes of this variability remain poorly understood. In addition to differences in intrinsic fidelity or error correction capability, viral mutation rates may be dependent on host factors. Here, we assessed the effect of the cellular environment on the rate of spontaneous mutation of the vesicular stomatitis virus (VSV), which has a broad host range and cell tropism. Luria-Delbrück fluctuation tests and sequencing showed that VSV mutated similarly…
2-(2,6-Dihalophenyl)-3-(pyrimidin-2-yl)-1,3-thiazolidin-4-ones as non-nucleoside HIV-1 reverse transcriptase inhibitors.
2004
Several 1,3-thiazolidin-4-ones bearing a 2,6-dihalophenyl group at C-2 and a substituted pyrimidin-2-yl ring at the N-3 were synthesised and evaluated as anti-HIV agents. The results of the in vitro tests showed that some of them were highly effective inhibitors of human immunodeficiency virus type-1 (HIV-1) replication at 10–40 nM concentrations with minimal cytotoxicity. Structure–activity relationship studies revealed that the nature of the substituents at the 2 and 3 positions of the thiazolidinone nucleus had a significant impact on the in vitro anti-HIV activity of this class of potent antiretroviral agents. The compounds had significantly reduced activity against the characteristic N…
Toward mass producible ordered bulk heterojunction organic photovoltaic devices.
2012
A strategy to fabricate nanostructured poly(3-hexylthiophene) (P3HT) films for organic photovoltaic (OPV) cells by a direct transfer method from a reusable soft replica mold is presented. The flexible polyfluoropolyether (PFPE) replica mold allows low-pressure and low- temperature process condition for the successful transfer of nanostructured P3HT films onto PEDOT/PSS-coated ITO substrates. To reduce the fabrication cost of masters in large area, we employed well-ordered anodic aluminum oxide (AAO) as a template. Also, we provide a method to fabricate reversed nanostructures by exploiting the self-replication of replica molds. The concept of the transfer method in low temperature with a fl…
Risk factors and interventional strategies for BK polyomavirus infection after renal transplantation.
2012
BK virus (BKV)-induced viraemia after renal transplantation can be associated with severe impairment of graft function. This study evaluated possible risk factors for BKV replication and examined the outcomes following various currently used treatment approaches.Fifty-seven renal transplant recipients with BKV viraemia were retrospectively compared with 71 BKV-negative recipients to identify risk factors for BKV viraemia. Furthermore, outcome and graft function in 14 patients with BKV replication, in whom mycophenolate mofetil (MMF) was discontinued with a dose reduction of the remaining immunosuppressants, were compared with 32 patients in whom both MMF and the additional immunosuppressant…
Non-local multiscale approach for the impact of go or grow hypothesis on tumour-viruses interactions
2021
International audience; We propose and study computationally a novel non-local multiscale moving boundary mathematical model for tumour and oncolytic virus (OV) interactions when we consider the go or grow hypothesis for cancer dynamics. This spatio-temporal model focuses on two cancer cell phenotypes that can be infected with the OV or remain uninfected, and which can either move in response to the extracellular-matrix (ECM) density or proliferate. The interactions between cancer cells, those among cancer cells and ECM, and those among cells and OV occur at the macroscale. At the micro-scale, we focus on the interactions between cells and matrix degrading enzymes (MDEs) that impact the mov…
All-fiber based chaotic polarization scrambler
2014
We present a fiber-based polarization scrambler founded on the nonlinear interaction between a signal and its backward replica generated and amplified by a reflective loop. The output polarization dynamic turns out to be chaotic.
The nucleosomal repeat length of pea (Pisum sativum) chromatin changes during germination
1985
Pea (Pisum sativum) nuclei have been isolated from ungerminated embryos, developing embryonic axes and seedlings. Morphological and biochemical criteria revealed that preparations were free from contaminants and that nuclei were intact. These circumstances permitted an accurate determination of nucleosomal repeat lengths, the values obtained being 175±4 base pairs for ungerminated embryos, 185±5 base pairs for 62-hours germinated embryonic axes and 185±3 base pairs for 6-day old seedlings. The results seem to indicate that the increase in repeat length is associated with the onset of transcription and/or replication of DNA.
Are replicate evaluations of triangle tests during a session good practice?
1997
Results from four experiments in which replicated triangle tests were performed are reported. Two experiments were carried out with non experienced assessors and the two other ones with experienced assessors. Results from the non experienced assessors showed a slight performance increase from the beginning to the end of the session whereas results from the experienced assessors did not. This is explained by an attentional process allowing non experienced assessors to gradually focus their attention on the difference between the two tested products. In some specific occasions, replicate triangle tests might be a good methodological practice when the purpose of the test is to study the effect…