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Carmen F Fioravanti - One of the best experts on this subject based on the ideXlab platform.

  • effects of plant flavonoids on manduca sexta tobacco hornworm fifth larval instar midgut and fat body mitochondrial transhydrogenase
    Archives of Insect Biochemistry and Physiology, 2012
    Co-Authors: Kurt P Vandock, Martin J Mitchell, Carmen F Fioravanti
    Abstract:

    : The reversible, membrane-associated transhydrogenase that catalyzes hydride-ion transfer between NADP(H) and NAD(H) was evaluated and compared to the corresponding NADH oxidase and succinate dehydrogenase activities in midgut and fat body mitochondria from fifth larval instar Manduca sexta. The developmentally significant NADPH-forming transhydrogenation occurs as a Nonenergy- or energy-linked activity with energy for the latter derived from either electron transport-dependent NADH or succinate utilization, or ATP hydrolysis by Mg++-dependent ATPase. In general, the plant flavonoids examined (chyrsin, juglone, morine, quercetin, and myricetin) affected all reactions in a dose-dependent fashion. Differences in the responses to the flavonoids were apparent, with the most notable being inhibition of midgut, but stimulation of fat body transhydrogenase by morin, and myricetin as also noted for NADH oxidase and succinate dehydrogenase. Although quercetin inhibited or stimulated transhydrogenase activity depending on the origin of mitochondria, it was without effect on either midgut or fat body NADH oxidase or succinate dehydrogenase. Observed sonication-dependent increases in flavonoid inhibition may well reflect an alteration in membrane configuration, resulting in increased exposure of the enzyme systems to the flavonoids. The effects of flavonoids on the transhydrogenation, NADH oxidase, and succinate dehydrogenase reactions suggest that compounds of this nature may prove valuable in the control of insect populations by affecting these mitochondrial enzyme components.

  • midgut and fatbody mitochondrial transhydrogenase activities during larval pupal development of the tobacco hornworm manduca sexta
    Journal of Insect Physiology, 2010
    Co-Authors: Kurt P Vandock, Stan L Smith, Christopher A Drummond, Carmen F Fioravanti
    Abstract:

    Abstract Midgut and fatbody mitochondria from fifth larval instar Manduca sexta display a membrane-associated transhydrogenase that catalyzes a reversible hydride ion transfer between NADP(H) and NAD(H). The NADPH-forming activity occurs as a Nonenergy- or energy-linked activity with energy for the latter derived from either electron transport-dependent NADH or succinate utilization, or ATP hydrolysis by Mg++-dependent ATPase. During the ten-day developmental period preceding the larval-pupal molt (fifth larval instar), significant peaks in the mitochondrial transhydrogenase activities of midgut and fatbody tissues were noted and these peaks were coincident with the onset of wandering behavior and with the fifty-fold increase in ecdysone 20-monooxygenase (E20-M) activity previously reported for M. sexta midgut. Since E20-M preferentially uses NADPH in catalyzing ecdysone conversion to the physiologically active molting hormone, 20-hydroxyecdysone, the physiological and developmental significance of the mitochondrial, NADPH-forming energy-linked transhydrogenations were made apparent. Moreover, that the increases in all transhydrogenase activities resulted from de novo enzyme synthesis were indicated by the cycloheximide-dependent reductions in these activities.

  • midgut mitochondrial transhydrogenase in wandering stage larvae of the tobacco hornworm manduca sexta
    Archives of Insect Biochemistry and Physiology, 2008
    Co-Authors: Kurt P Vandock, Stan L Smith, Carmen F Fioravanti
    Abstract:

    Midgut mitochondria from fifth larval instar Manduca sexta exhibited a transhydrogenase that catalyzes the following reversible reaction: NADPH + NAD+ NADP+ + NADH. The NADPH-forming transhydrogenation occurred as a Nonenergy- and energy-linked activity. Energy for the latter was derived from the electron transport–dependent utilization of NADH or succinate, or from Mg++-dependent ATP hydrolysis by ATPase. The NADH-forming and all of the NADPH-forming reactions appeared optimal at pH 7.5, were stable to prolonged dialysis, and displayed thermal lability. N,N′-dicyclohexylcarbodiimide (DCCD) inhibited the NADPH NAD+ and energy-linked NADH NADP+ transhydrogenations, but not the Nonenergy-linked NADH NADP+ reaction. Oligomycin only inhibited the ATP-dependent energy-linked activity. The NADH-forming, Nonenergy-linked NADPH-forming, and the energy-linked NADPH-forming activities were membrane-associated in M. sexta mitochondria. This is the first demonstration of the reversibility of the M. sexta mitochondrial transhydrogenase and, more importantly, the occurrence of Nonenergy-linked and energy-linked NADH NADP+ transhydrogenations. The potential relationship of the transhydrogenase to the mitochondrial, NADPH-utilizing ecdysone-20 monooxygenase of M. sexta is considered. Arch. Insect Biochem. Physiol. 69:118-126, 2008. © 2008 Wiley-Liss, Inc.

Tomas Výrost - One of the best experts on this subject based on the ideXlab platform.

  • connectedness between energy and Nonenergy commodity markets evidence from quantile coherency networks
    Resources Policy, 2021
    Co-Authors: Rabeh Khalfaoui, Eduard Baumohl, Suleman Sarwar, Tomas Výrost
    Abstract:

    Abstract The worldwide economy has experienced several changes in energy and Nonenergy prices. This has motivated academics, investors, and policymakers to analyze the relationships between energy and Nonenergy commodity markets. In this study, a novel approach of quantile coherency is used to examine the dependence structure between energy and Nonenergy commodity pairs at different frequencies and quantiles in their joint return distribution over the period 1960:M1–2019:M10. Overall, the empirical findings illustrate evidence of a low significant dependency between energy and Nonenergy commodity markets across different frequencies and quantiles. In addition, our findings show that some Nonenergy commodity markets have a neutral relationship with global energy commodity markets.

J. Meng - One of the best experts on this subject based on the ideXlab platform.

  • Spin-Isospin Resonances: A Self-Consistent Covariant Description
    Physical Review Letters, 2008
    Co-Authors: H. Liang, N. Van Giai, J. Meng
    Abstract:

    For the first time a fully self-consistent charge-exchange relativistic RPA based on the relativistic Hartree-Fock (RHF) approach is established. The self-consistency is verified by the so-called isobaric analog state (IAS) check. The excitation properties and the Nonenergy weighted sum rules of two important charge-exchange excitation modes, the Gamow-Teller resonance (GTR) and the spin-dipole resonance (SDR), are well reproduced in the doubly magic nuclei 48Ca, 90Zr and 208Pb without readjustment of the particle-hole residual interaction. The dominant contribution of the exchange diagrams is demonstrated.

Kurt P Vandock - One of the best experts on this subject based on the ideXlab platform.

  • effects of plant flavonoids on manduca sexta tobacco hornworm fifth larval instar midgut and fat body mitochondrial transhydrogenase
    Archives of Insect Biochemistry and Physiology, 2012
    Co-Authors: Kurt P Vandock, Martin J Mitchell, Carmen F Fioravanti
    Abstract:

    : The reversible, membrane-associated transhydrogenase that catalyzes hydride-ion transfer between NADP(H) and NAD(H) was evaluated and compared to the corresponding NADH oxidase and succinate dehydrogenase activities in midgut and fat body mitochondria from fifth larval instar Manduca sexta. The developmentally significant NADPH-forming transhydrogenation occurs as a Nonenergy- or energy-linked activity with energy for the latter derived from either electron transport-dependent NADH or succinate utilization, or ATP hydrolysis by Mg++-dependent ATPase. In general, the plant flavonoids examined (chyrsin, juglone, morine, quercetin, and myricetin) affected all reactions in a dose-dependent fashion. Differences in the responses to the flavonoids were apparent, with the most notable being inhibition of midgut, but stimulation of fat body transhydrogenase by morin, and myricetin as also noted for NADH oxidase and succinate dehydrogenase. Although quercetin inhibited or stimulated transhydrogenase activity depending on the origin of mitochondria, it was without effect on either midgut or fat body NADH oxidase or succinate dehydrogenase. Observed sonication-dependent increases in flavonoid inhibition may well reflect an alteration in membrane configuration, resulting in increased exposure of the enzyme systems to the flavonoids. The effects of flavonoids on the transhydrogenation, NADH oxidase, and succinate dehydrogenase reactions suggest that compounds of this nature may prove valuable in the control of insect populations by affecting these mitochondrial enzyme components.

  • midgut and fatbody mitochondrial transhydrogenase activities during larval pupal development of the tobacco hornworm manduca sexta
    Journal of Insect Physiology, 2010
    Co-Authors: Kurt P Vandock, Stan L Smith, Christopher A Drummond, Carmen F Fioravanti
    Abstract:

    Abstract Midgut and fatbody mitochondria from fifth larval instar Manduca sexta display a membrane-associated transhydrogenase that catalyzes a reversible hydride ion transfer between NADP(H) and NAD(H). The NADPH-forming activity occurs as a Nonenergy- or energy-linked activity with energy for the latter derived from either electron transport-dependent NADH or succinate utilization, or ATP hydrolysis by Mg++-dependent ATPase. During the ten-day developmental period preceding the larval-pupal molt (fifth larval instar), significant peaks in the mitochondrial transhydrogenase activities of midgut and fatbody tissues were noted and these peaks were coincident with the onset of wandering behavior and with the fifty-fold increase in ecdysone 20-monooxygenase (E20-M) activity previously reported for M. sexta midgut. Since E20-M preferentially uses NADPH in catalyzing ecdysone conversion to the physiologically active molting hormone, 20-hydroxyecdysone, the physiological and developmental significance of the mitochondrial, NADPH-forming energy-linked transhydrogenations were made apparent. Moreover, that the increases in all transhydrogenase activities resulted from de novo enzyme synthesis were indicated by the cycloheximide-dependent reductions in these activities.

  • midgut mitochondrial transhydrogenase in wandering stage larvae of the tobacco hornworm manduca sexta
    Archives of Insect Biochemistry and Physiology, 2008
    Co-Authors: Kurt P Vandock, Stan L Smith, Carmen F Fioravanti
    Abstract:

    Midgut mitochondria from fifth larval instar Manduca sexta exhibited a transhydrogenase that catalyzes the following reversible reaction: NADPH + NAD+ NADP+ + NADH. The NADPH-forming transhydrogenation occurred as a Nonenergy- and energy-linked activity. Energy for the latter was derived from the electron transport–dependent utilization of NADH or succinate, or from Mg++-dependent ATP hydrolysis by ATPase. The NADH-forming and all of the NADPH-forming reactions appeared optimal at pH 7.5, were stable to prolonged dialysis, and displayed thermal lability. N,N′-dicyclohexylcarbodiimide (DCCD) inhibited the NADPH NAD+ and energy-linked NADH NADP+ transhydrogenations, but not the Nonenergy-linked NADH NADP+ reaction. Oligomycin only inhibited the ATP-dependent energy-linked activity. The NADH-forming, Nonenergy-linked NADPH-forming, and the energy-linked NADPH-forming activities were membrane-associated in M. sexta mitochondria. This is the first demonstration of the reversibility of the M. sexta mitochondrial transhydrogenase and, more importantly, the occurrence of Nonenergy-linked and energy-linked NADH NADP+ transhydrogenations. The potential relationship of the transhydrogenase to the mitochondrial, NADPH-utilizing ecdysone-20 monooxygenase of M. sexta is considered. Arch. Insect Biochem. Physiol. 69:118-126, 2008. © 2008 Wiley-Liss, Inc.

H. Liang - One of the best experts on this subject based on the ideXlab platform.

  • Spin-Isospin Resonances: A Self-Consistent Covariant Description
    Physical Review Letters, 2008
    Co-Authors: H. Liang, N. Van Giai, J. Meng
    Abstract:

    For the first time a fully self-consistent charge-exchange relativistic RPA based on the relativistic Hartree-Fock (RHF) approach is established. The self-consistency is verified by the so-called isobaric analog state (IAS) check. The excitation properties and the Nonenergy weighted sum rules of two important charge-exchange excitation modes, the Gamow-Teller resonance (GTR) and the spin-dipole resonance (SDR), are well reproduced in the doubly magic nuclei 48Ca, 90Zr and 208Pb without readjustment of the particle-hole residual interaction. The dominant contribution of the exchange diagrams is demonstrated.