The Experts below are selected from a list of 279 Experts worldwide ranked by ideXlab platform
Deoki N Tripathy - One of the best experts on this subject based on the ideXlab platform.
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generation of thymidine kinase deficient mutants of infectious laryngotracheitis virus
Virology, 1995Co-Authors: William M Schnitzlein, R Winans, S Ellsworth, Deoki N TripathyAbstract:Abstract Current vaccines for the avian respiratory disease infectious laryngotracheitis consist of naturally attenuated strains of the causative agent—the herpesvirus infectious laryngotracheitis virus (ILTV). Due to the dissemination of these viruses from vaccinated chickens as well as their possible reversion to more pathogenic forms, the use of genetically engineered viral vaccines lacking virulence factors while retaining antigenicity is being considered. Since the thymidine kinase (TK) activity of herpesviruses has been associated with virulence, inactivation of the encoding gene in the ILTV genome should attenuate the virus. Moreover, by analogy to other TK - herpesviruses, the ability of such ILTV mutants to induce a protective response in chickens should not be compromised. Therefore, the deliberate genetic alteration of ILTV was attempted. In order to prevent reversion and also to enable identification of the modified virus, a "marker" transcriptional unit ( Escherichia coli lacZ gene fused to a SV-40 3′-polyadenylation signal sequence and regulated by the pseudorabies virus gX gene promoter) was inserted via homologous recombination at one of two loci within the ILTV TK gene. Recombinant viruses were identified and plaque-purified on the basis of their ability to produce β-galactosidase. Retention of the foreign DNA at the predicted sites in the genomes of the recombinant ILTV was verified by Southern hybridization. Since their replication was unaffected by the thymine analog 1-(2-fluoro-2-deoxy-β- d -arabinofuranosyl)-5-methyluracil, the recombinants appeared to have a TK - phenotype. Despite this apparent deficiency, prior inoculation of either recombinant virus into chickens afforded the birds protection against a lethal challenge of virulent ILTV. Moreover, the degree of respiratory distress in the chickens vaccinated with the recombinants was relatively mild compared to the severe reaction in birds receiving the parental virus. Thus, ILTV can be genetically attenuated without an accompanying loss of immunogenicity.
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generation of thymidine kinase deficient mutants of infectious laryngotracheitis virus
Virology, 1995Co-Authors: William M Schnitzlein, R Winans, S Ellsworth, Deoki N TripathyAbstract:Current vaccines for the avian respiratory disease infectious laryngotrachetitis consist of naturally attenuated strains of the causative agent--the herpesvirus infectious laryngotracheitis virus (ILTV). Due to the dissemination of these viruses from vaccinated chickens as well as their possible reversion to more pathogenic forms, the use of genetically engineered viral vaccines lacking virulence factors while retaining antigenicity is being considered. Since the thymidine kinase (TK) activity of herpesviruses has been associated with virulence, inactivation of the encoding gene in the ILTV genome should attenuate the virus. Moreover, by analogy to other TK- herpesviruses, the ability of such ILTV mutants to induce a protective response in chickens should not be compromised. Therefore, the deliberate genetic alteration of ILTV was attempted. In order to prevent reversion and also to enable identification of the modified virus, a "marker" transcriptional unit (Escherichia coli lacZ gene fused to a SV-40 3'-polyadenylation signal sequence and regulated by the pseudorabies virus gX gene promoter) was inserted via homologous recombination at one of two loci within the ILTV TK gene. Recombinant viruses were identified and plaque-purified on the basis of their ability to produce beta-galactosidase. Retention of the foreign DNA at the predicted sites in the genomes of the recombinant ILTV was verified by Southern hybridization. Since their replication was unaffected by the thymine analog 1-(2-fluoro-2-deoxy-beta-D-arabinofuranosyl)-5-methyluracil, the recombinants appeared to have a TK- phenotype. Despite this apparent deficiency, prior inoculation of either recombinant virus into chickens afforded the birds protection against a lethal challenge of virulent ILTV. Moreover, the degree of respiratory distress in the chickens vaccinated with the recombinants was relatively mild compared to the severe reaction in birds receiving the parental virus. Thus, ILTV can be genetically attenuated without an accompanying loss of immunogenicity.
William M Schnitzlein - One of the best experts on this subject based on the ideXlab platform.
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generation of thymidine kinase deficient mutants of infectious laryngotracheitis virus
Virology, 1995Co-Authors: William M Schnitzlein, R Winans, S Ellsworth, Deoki N TripathyAbstract:Abstract Current vaccines for the avian respiratory disease infectious laryngotracheitis consist of naturally attenuated strains of the causative agent—the herpesvirus infectious laryngotracheitis virus (ILTV). Due to the dissemination of these viruses from vaccinated chickens as well as their possible reversion to more pathogenic forms, the use of genetically engineered viral vaccines lacking virulence factors while retaining antigenicity is being considered. Since the thymidine kinase (TK) activity of herpesviruses has been associated with virulence, inactivation of the encoding gene in the ILTV genome should attenuate the virus. Moreover, by analogy to other TK - herpesviruses, the ability of such ILTV mutants to induce a protective response in chickens should not be compromised. Therefore, the deliberate genetic alteration of ILTV was attempted. In order to prevent reversion and also to enable identification of the modified virus, a "marker" transcriptional unit ( Escherichia coli lacZ gene fused to a SV-40 3′-polyadenylation signal sequence and regulated by the pseudorabies virus gX gene promoter) was inserted via homologous recombination at one of two loci within the ILTV TK gene. Recombinant viruses were identified and plaque-purified on the basis of their ability to produce β-galactosidase. Retention of the foreign DNA at the predicted sites in the genomes of the recombinant ILTV was verified by Southern hybridization. Since their replication was unaffected by the thymine analog 1-(2-fluoro-2-deoxy-β- d -arabinofuranosyl)-5-methyluracil, the recombinants appeared to have a TK - phenotype. Despite this apparent deficiency, prior inoculation of either recombinant virus into chickens afforded the birds protection against a lethal challenge of virulent ILTV. Moreover, the degree of respiratory distress in the chickens vaccinated with the recombinants was relatively mild compared to the severe reaction in birds receiving the parental virus. Thus, ILTV can be genetically attenuated without an accompanying loss of immunogenicity.
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generation of thymidine kinase deficient mutants of infectious laryngotracheitis virus
Virology, 1995Co-Authors: William M Schnitzlein, R Winans, S Ellsworth, Deoki N TripathyAbstract:Current vaccines for the avian respiratory disease infectious laryngotrachetitis consist of naturally attenuated strains of the causative agent--the herpesvirus infectious laryngotracheitis virus (ILTV). Due to the dissemination of these viruses from vaccinated chickens as well as their possible reversion to more pathogenic forms, the use of genetically engineered viral vaccines lacking virulence factors while retaining antigenicity is being considered. Since the thymidine kinase (TK) activity of herpesviruses has been associated with virulence, inactivation of the encoding gene in the ILTV genome should attenuate the virus. Moreover, by analogy to other TK- herpesviruses, the ability of such ILTV mutants to induce a protective response in chickens should not be compromised. Therefore, the deliberate genetic alteration of ILTV was attempted. In order to prevent reversion and also to enable identification of the modified virus, a "marker" transcriptional unit (Escherichia coli lacZ gene fused to a SV-40 3'-polyadenylation signal sequence and regulated by the pseudorabies virus gX gene promoter) was inserted via homologous recombination at one of two loci within the ILTV TK gene. Recombinant viruses were identified and plaque-purified on the basis of their ability to produce beta-galactosidase. Retention of the foreign DNA at the predicted sites in the genomes of the recombinant ILTV was verified by Southern hybridization. Since their replication was unaffected by the thymine analog 1-(2-fluoro-2-deoxy-beta-D-arabinofuranosyl)-5-methyluracil, the recombinants appeared to have a TK- phenotype. Despite this apparent deficiency, prior inoculation of either recombinant virus into chickens afforded the birds protection against a lethal challenge of virulent ILTV. Moreover, the degree of respiratory distress in the chickens vaccinated with the recombinants was relatively mild compared to the severe reaction in birds receiving the parental virus. Thus, ILTV can be genetically attenuated without an accompanying loss of immunogenicity.
Shunichi Kawahara - One of the best experts on this subject based on the ideXlab platform.
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theoretical investigation on the substitution effect of the hydrogen bond energy of the watson crick type base pair between substituted 1 methyluracil and 9 methyladenine
Journal of Molecular Structure-theochem, 2002Co-Authors: Shunichi Kawahara, Tadafumi UchimaruAbstract:Abstract Basis set effect in evaluation of base pair formation energy of the Watson–Crick type base pair between substituted 1-methyluracil and 9-methyladenine was studied in the Hartree–Fock and second-order Moller–Plesset level of theory. The same trend was observed in the substitution effect in all basis sets attempted; thus, the error depending on the basis set incompleteness is minimal in the evaluation of the substitution effect of the base pair formation energy. Neither the hydrogen bond distance nor the atomic charge was a valid index for the hydrogen bond status in base pairing.
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ab initio evaluation of the substitution effect of the hydrogen bond energy of the watson crick type base pair between 1 methyluracil and substituted 9 methyladenine derivatives
Journal of Physical Chemistry A, 2001Co-Authors: Shunichi Kawahara, Tadafumi Uchimaru, Kazunari Taira, Mitsuo SekineAbstract:Shun-ichi Kawahara,† Tadafumi Uchimaru,*,‡ Kazunari Taira,† and Mitsuo Sekine§ Research Center of Gene DiscoVery, National Institute of AdVanced Industrial Science and Technology, Tsukuba, Ibaraki 305-8562, Japan, Research Institute for Computational Sciences, National Institute of AdVanced Industrial Science and Technology, Tsukuba, Ibaraki 305-8568, Japan, and Department of Life Science, Faculty of Bioscience and Biotechnology, Tokyo Institute of Technology, Nagatsuta, Midori-ku, Yokohama 226-8501, Japan
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evaluation of the hydrogen bond energy of base pairs formed between substituted 9 methyladenine derivatives and 1 methyluracil by use of molecular orbital theory
Nucleic acids symposium series, 2000Co-Authors: Shunichi Kawahara, Kazunari Taira, Mitsuo Sekine, Tadafumi UchimaruAbstract:Systematic substituent effects on the stability of the hydrogen bonding between substituted 9-methyladenine derivatives (Ax) and 1-methyluracil (U) were studied by ab initio molecular orbital theory. Predicted substituent effects on the hydrogen bond energies of Ax-U base pairs were in good agreement with those observed for experimental binding constants. Ab initio calculation is effective for evaluation of the stability of the hydrogen-bonding pairs of chemically modified nucleic acid base analogues. In contrast to the substitution effect of uracil on hydrogen bond energies of A-Ux base pairs, it is difficult to systematically interpret the substitution effect of adenine derivatives for Ax-U base pairs.
Tadafumi Uchimaru - One of the best experts on this subject based on the ideXlab platform.
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theoretical investigation on the substitution effect of the hydrogen bond energy of the watson crick type base pair between substituted 1 methyluracil and 9 methyladenine
Journal of Molecular Structure-theochem, 2002Co-Authors: Shunichi Kawahara, Tadafumi UchimaruAbstract:Abstract Basis set effect in evaluation of base pair formation energy of the Watson–Crick type base pair between substituted 1-methyluracil and 9-methyladenine was studied in the Hartree–Fock and second-order Moller–Plesset level of theory. The same trend was observed in the substitution effect in all basis sets attempted; thus, the error depending on the basis set incompleteness is minimal in the evaluation of the substitution effect of the base pair formation energy. Neither the hydrogen bond distance nor the atomic charge was a valid index for the hydrogen bond status in base pairing.
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ab initio evaluation of the substitution effect of the hydrogen bond energy of the watson crick type base pair between 1 methyluracil and substituted 9 methyladenine derivatives
Journal of Physical Chemistry A, 2001Co-Authors: Shunichi Kawahara, Tadafumi Uchimaru, Kazunari Taira, Mitsuo SekineAbstract:Shun-ichi Kawahara,† Tadafumi Uchimaru,*,‡ Kazunari Taira,† and Mitsuo Sekine§ Research Center of Gene DiscoVery, National Institute of AdVanced Industrial Science and Technology, Tsukuba, Ibaraki 305-8562, Japan, Research Institute for Computational Sciences, National Institute of AdVanced Industrial Science and Technology, Tsukuba, Ibaraki 305-8568, Japan, and Department of Life Science, Faculty of Bioscience and Biotechnology, Tokyo Institute of Technology, Nagatsuta, Midori-ku, Yokohama 226-8501, Japan
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evaluation of the hydrogen bond energy of base pairs formed between substituted 9 methyladenine derivatives and 1 methyluracil by use of molecular orbital theory
Nucleic acids symposium series, 2000Co-Authors: Shunichi Kawahara, Kazunari Taira, Mitsuo Sekine, Tadafumi UchimaruAbstract:Systematic substituent effects on the stability of the hydrogen bonding between substituted 9-methyladenine derivatives (Ax) and 1-methyluracil (U) were studied by ab initio molecular orbital theory. Predicted substituent effects on the hydrogen bond energies of Ax-U base pairs were in good agreement with those observed for experimental binding constants. Ab initio calculation is effective for evaluation of the stability of the hydrogen-bonding pairs of chemically modified nucleic acid base analogues. In contrast to the substitution effect of uracil on hydrogen bond energies of A-Ux base pairs, it is difficult to systematically interpret the substitution effect of adenine derivatives for Ax-U base pairs.
Changkoo Shim - One of the best experts on this subject based on the ideXlab platform.
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the transport of a reversible proton pump antagonist 5 6 dimethyl 2 4 fluorophenylamino 4 1 methyl 1 2 3 4 tetrahydroisoquinoline 2 yl pyrimidine hydrochloride yh1885 across caco 2 cell monolayers
Drug Metabolism and Disposition, 2001Co-Authors: Sukjae Chung, Dongchool Kim, Hyunsoo Kim, Jongwook Lee, Changkoo ShimAbstract:5,6-Dimethyl-2-(4-fluorophenylamino)-4-(1-methyl-1,2,3,4-tetrahydroisoquinoline-2-yl) pyrimidine hydrochloride (YH1885) is under development as a novel acid pump antagonist by Yuhan Research Center. Previous studies have suggested that the AUC and Cmax of orally dosed YH1885 are dose-dependent in the range of 2 to 500 mg/kg. The objective of the present study was to investigate the absorption mechanism of YH1885 using a human colon carcinoma cell line, Caco-2. The cells were grown to confluency on a permeable polycarbonate membrane insert to permit loading of YH1885 on either the apical or basolateral side of the cell monolayer. The flux across the monolayer from the apical to basolateral side was 3 to 5 times greater than that from the basolateral to apical side. The uptake of YH1885 into the Caco-2 cell monolayer was saturable and appeared to be mediated by a high-affinity transporter, with an apparentKm of 1.47 ± 0.21 μM and aVmax of 25.14 ± 1.16 pmol/cm2/40 s. The apical to basolateral transport across the monolayer was Na+-independent, H+-sensitive, and energy-dependent. The transport was inhibited significantly by the presence of structural analogs of YH1885 (e.g., YH957, YH1070, and YH1041), some pyrimidine nucleobases (uracil and 5-methyluracil), and nucleobase transport inhibitors (e.g., papaverine, dipyridamole, and phloridzin). These results demonstrate that the apical to basolateral transport of YH1885 across the Caco-2 cell monolayer is partially mediated by a nucleobase transport system, which exhibits high-affinity and energy-dependent properties for YH1885. Saturation of this transport system, in addition to the limited solubility of YH1885 (i.e., ∼5.3 μM), appears to contribute to the dose-dependent bioavailability of the drug.