The Experts below are selected from a list of 695040 Experts worldwide ranked by ideXlab platform
Dorothea L. Sawicki - One of the best experts on this subject based on the ideXlab platform.
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Coronavirus Transcription: A Perspective
Current topics in microbiology and immunology, 2005Co-Authors: Stanley G. Sawicki, Dorothea L. SawickiAbstract:At the VIth International Symposium on Corona and Related Viruses held in Quebec, Canada in 1994 we presented a new model for coronavirus transcription to explain how subgenome-length minus Strands, which are used as templates for the synthesis of subgenomic mRNAs, might arise by a process involving discontinuous RNA synthesis. The old model explaining subgenomic mRNA synthesis, which was called leader-primed transcription, was based on erroneous evidence that only genome-length negative Strands were present in replicative intermediates. To explain the discovery of subgenome-length minus Strands, a related model, called the replicon model, was proposed: The subgenomic mRNAs would be produced initially by leader-primed transcription and then replicated into minus-strand templates that would in turn be transcribed into subgenomic mRNAs. We review the experimental evidence that led us to formulate a third model proposing that the discontinuous event in coronavirus RNA synthesis occurs during minus strand synthesis. With our model the genome is copied both continuously to produce minus-strand templates for genome RNA synthesis and discontinuously to produce minus-strand templates for subgenomic mRNA synthesis, and the subgenomic mRNAs do not function as templates for minus strand synthesis, only the genome does.
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Alphavirus Minus-Strand Synthesis and Persistence in Mouse Embryo Fibroblasts Derived from Mice Lacking RNase L and Protein Kinase R
Journal of Virology, 2003Co-Authors: Dorothea L. Sawicki, Bryan R.g. Williams, Robert H. Silverman, Stanley G. SawickiAbstract:We report our studies to probe the possible role of the host response to double-stranded RNA in cessation of alphavirus minus-strand synthesis. Mouse embryo fibroblasts (MEF) from Mx1-deficient mice that also lack either the protein kinase R (PKR) or the latent RNase L or both PKR and RNase L were screened. In RNase L-deficient but not wild-type or PKR-deficient MEF, there was continuous synthesis of minus-strand templates and the formation of new replication complexes producing viral plus Strands. Inhibiting translation caused minus-strand synthesis to stop and a loss of transcription activity of the mature replication complexes. This turnover of replication complexes that were stable in cells containing RNase L suggested that RNase L plays some role, albeit possibly indirect, in the formation of stable replication complexes during alphavirus infection. In addition, confluent monolayers of RNase L-deficient murine cells readily established persistent infections and were not killed. This phenotype is contrary to what has been observed for infection in vertebrate cells with a presumably functional RNase L gene and more resembled alphavirus replication in Aedes mosquito cells, in which the activity of replication complexes making plus stands was also found to decay with inhibition of translation.
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Coronaviruses use Discontinuous Extension for Synthesis of Subgenome-Length Negative Strands
Advances in experimental medicine and biology, 1995Co-Authors: Stanley G. Sawicki, Dorothea L. SawickiAbstract:We have developed a new model for coronavirus transcription, which we call discontinuous extension, to explain how subgenome-length negatives stands are derived directly from the genome. The current model called leader-primed transcription, which states that subgenomic mRNA is transcribed directly from genome-length negative-Strands, cannot explain many of the recent experimental findings. For instance, subgenomic mRNAs are transcribed directly via transcription intermediates that contain subgenome-length negative-strand templates; however subgenomic mRNA does not appear to be copied directly into negatives Strands. In our model the subgenome-length negative Strands would be derived using the genome as a template. After the polymerase had copied the 3′-end of the genome, it would detach at any one of the several intergenic sequences and reattach to the sequence immediately downstream of the leader sequence at the 5′-end of genome RNA. Base pairing between the 3′-end of the nascent subgenome-length negative Strands, which would be complementary to the intergenic sequence at the end of the leader sequence at the 5′-end of genome, would serve to align the nascent negative strand to the genome and permit the completion of synthesis, i.e., discontinuous extension of the 3′-end of the negative strand. Thus, subgenome-length negative-Strands would arise by discontinuous synthesis, but of negative Strands, not of positive Strands as proposed originally by the leader-primed transcription model.
Osami Tsukamoto - One of the best experts on this subject based on the ideXlab platform.
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Measurement of Current Distribution in Superconducting Non-Insulated Stranded Cable
Advances in cryogenic engineering, 1996Co-Authors: Naoyuki Amemiya, N. Tsuchioka, Osami TsukamotoAbstract:A method to measure the current distribution in superconducting stranded-cables without electrical insulation has been developed. Stability property of multi-strand superconducting cables is significantly influenced by the current distribution among their Strands. Static current imbalance among the Strands is one of the reasons for the quench current degradation in multi-strand superconducting cables. In addition to this static current distribution, we point out the transient current re-distribution during quench or recovery process can influence the stability of multi-strand superconducting cables. The measurement of current distribution in multi-strand superconducting cables is necessary to study their stability property experimentally. In our method, sets of Hall sensors arranged around the cable are used to measure the magnetic field distribution. The current in each strand is calculated with the measured magnetic field. It is possible to measure the static current distribution as well as transient one. With this method, the current distribution can be measured locally in superconducting cables made of Strands without insulation where the current distribution is supposed to change along the cable axis.
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Stability analysis of multi-strand superconducting cables
IEEE Transactions on Applied Superconductivity, 1995Co-Authors: Naoyuki Amemiya, Osami TsukamotoAbstract:When a normal zone is produced in one or a few Strands in a multi-strand superconducting cable by a localized disturbance, the current in the normal-transited strand transfers to the others via contact resistance between Strands. Heat generated in the normal zone also diffuses to the other Strands. The stability of the multi-strand superconducting cable against local disturbances is much influenced by these current transfer and thermal diffusion. The influence of the copper resistivity on current transfer and stability is studied. When we plot the MQE on "contact resistivity"-"contact thermal conductivity"-plane, there are a stable region with large MQE and an unstable region with small MQE. The small contact resistance and small contact thermal conductivity between Strands are preferable from the view point of stability. If the contact thermal conductivity is small, the transition from the stable region to the unstable region is drastic. >
Young Hwan Park - One of the best experts on this subject based on the ideXlab platform.
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Analytical Model of Nonlinear Stress-Strain Relation for a Strand Made of Two Materials
Materials, 2017Co-Authors: Young Hwan ParkAbstract:Unlike conventional steel Strands, the smart strand supports strain-measuring function and adopts different materials for its core wire and helical wires. This study intends to analytically derive the nonlinear stress-strain model of this strand made of two materials. The effect of the bending moment and torsional moment of the helical wires on the overall load within the range of geometric shapes shown by actually used Strands is verified to be negligible and is thus ignored in order to simplify the analytical model. Moreover, the slight difference between the actual and analytic behaviors, which only appears in the slope varying part in the case of bilinear behavior, such as that of steel, is also ignored. The proposed constitutive model of the smart strand obtained by introducing the experimental stress-strain relation between the carbon fiber reinforced polymer core wire and the helical steel wires is in good agreement with the experimental data. The previous analytical models are applicable only to Strands made of a unique linear material, whereas the model proposed in this study is also applicable to Strands in which the core wire and the helical wires are made of two different materials, exhibiting nonlinear behavior.
Stanley G. Sawicki - One of the best experts on this subject based on the ideXlab platform.
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Coronavirus Transcription: A Perspective
Current topics in microbiology and immunology, 2005Co-Authors: Stanley G. Sawicki, Dorothea L. SawickiAbstract:At the VIth International Symposium on Corona and Related Viruses held in Quebec, Canada in 1994 we presented a new model for coronavirus transcription to explain how subgenome-length minus Strands, which are used as templates for the synthesis of subgenomic mRNAs, might arise by a process involving discontinuous RNA synthesis. The old model explaining subgenomic mRNA synthesis, which was called leader-primed transcription, was based on erroneous evidence that only genome-length negative Strands were present in replicative intermediates. To explain the discovery of subgenome-length minus Strands, a related model, called the replicon model, was proposed: The subgenomic mRNAs would be produced initially by leader-primed transcription and then replicated into minus-strand templates that would in turn be transcribed into subgenomic mRNAs. We review the experimental evidence that led us to formulate a third model proposing that the discontinuous event in coronavirus RNA synthesis occurs during minus strand synthesis. With our model the genome is copied both continuously to produce minus-strand templates for genome RNA synthesis and discontinuously to produce minus-strand templates for subgenomic mRNA synthesis, and the subgenomic mRNAs do not function as templates for minus strand synthesis, only the genome does.
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Alphavirus Minus-Strand Synthesis and Persistence in Mouse Embryo Fibroblasts Derived from Mice Lacking RNase L and Protein Kinase R
Journal of Virology, 2003Co-Authors: Dorothea L. Sawicki, Bryan R.g. Williams, Robert H. Silverman, Stanley G. SawickiAbstract:We report our studies to probe the possible role of the host response to double-stranded RNA in cessation of alphavirus minus-strand synthesis. Mouse embryo fibroblasts (MEF) from Mx1-deficient mice that also lack either the protein kinase R (PKR) or the latent RNase L or both PKR and RNase L were screened. In RNase L-deficient but not wild-type or PKR-deficient MEF, there was continuous synthesis of minus-strand templates and the formation of new replication complexes producing viral plus Strands. Inhibiting translation caused minus-strand synthesis to stop and a loss of transcription activity of the mature replication complexes. This turnover of replication complexes that were stable in cells containing RNase L suggested that RNase L plays some role, albeit possibly indirect, in the formation of stable replication complexes during alphavirus infection. In addition, confluent monolayers of RNase L-deficient murine cells readily established persistent infections and were not killed. This phenotype is contrary to what has been observed for infection in vertebrate cells with a presumably functional RNase L gene and more resembled alphavirus replication in Aedes mosquito cells, in which the activity of replication complexes making plus stands was also found to decay with inhibition of translation.
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Coronaviruses use Discontinuous Extension for Synthesis of Subgenome-Length Negative Strands
Advances in experimental medicine and biology, 1995Co-Authors: Stanley G. Sawicki, Dorothea L. SawickiAbstract:We have developed a new model for coronavirus transcription, which we call discontinuous extension, to explain how subgenome-length negatives stands are derived directly from the genome. The current model called leader-primed transcription, which states that subgenomic mRNA is transcribed directly from genome-length negative-Strands, cannot explain many of the recent experimental findings. For instance, subgenomic mRNAs are transcribed directly via transcription intermediates that contain subgenome-length negative-strand templates; however subgenomic mRNA does not appear to be copied directly into negatives Strands. In our model the subgenome-length negative Strands would be derived using the genome as a template. After the polymerase had copied the 3′-end of the genome, it would detach at any one of the several intergenic sequences and reattach to the sequence immediately downstream of the leader sequence at the 5′-end of genome RNA. Base pairing between the 3′-end of the nascent subgenome-length negative Strands, which would be complementary to the intergenic sequence at the end of the leader sequence at the 5′-end of genome, would serve to align the nascent negative strand to the genome and permit the completion of synthesis, i.e., discontinuous extension of the 3′-end of the negative strand. Thus, subgenome-length negative-Strands would arise by discontinuous synthesis, but of negative Strands, not of positive Strands as proposed originally by the leader-primed transcription model.
Howard Ochman - One of the best experts on this subject based on the ideXlab platform.
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Strand asymmetries in DNA evolution
Trends in genetics : TIG, 1997Co-Authors: M. Pilar Francino, Howard OchmanAbstract:The complementary Strands of DNA differ with respect to replication and transcription. Both of these processes are asymmetric and can bias the occurrence of mutations between the Strands: during replication, the discontinuous lagging strand undergoes certain errors at higher rates, and transcription overexposes the nontranscribed strand to DNA damage while targeting repair enzymes to the transcribed strand. While biases introduced during replication apparently have little impact on sequence evolution, the effects of transcription are observed in the asymmetric patterns of substitution in bacterial genes and might be influencing genome-wide patterns of base composition.
