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Jenkun Lin - One of the best experts on this subject based on the ideXlab platform.

  • Cancer Chemoprevention by Tea Polyphenols Through Modulating Signal Transduction Pathways
    Archives of Pharmacal Research, 2002
    Co-Authors: Jenkun Lin
    Abstract:

    The action mechanisms of several chemopreventive agents derived from herbal medicine and edible plants have become attractive issues in cancer research. Tea is the most widely consumed beverage worldwide. Recently, the cancer chemopreventive actions of tea have been intensively investigated. It have been demonstrated that the active principles of tea were attributed to their tea polyphenols. Recently, tremendous progress has been made in elucidating the molecular mechanisms of cancer chemoprevention by tea and tea polyphenols. The suppression of various tumor biomarkers including growth factor receptor tyrosine kinases, cytokine receptor kinases, PI3K, phosphatases, ras, raf, MAPK cascades, N · FB, I · B kinase, PKA, PKB, PKC, c-jun, c-fos, c-myc, cdks, cyclins, and related transducing proteins by tea polyphenols has been studied in our laboratory and others. The I · B kinase (IKK) activity in LPS-acti-ated murine macrophages (RAW 264.7 cells) was found to be inhibited by various tea polyphenols including (−) epigallocatechin-3-gallate (EGCG), theaflavin (TF-1), theaflavin-3-gal-late (TF-2) and theaflavin-3,3′-digallate (TF-3). TF-3 inhibited IKK activity in activated macrophages more strongly than did the other tea polyphenols. TF-3 inhibited both IKK1 and IKK2 activity and prevented the degradation of I · B · and I · B · in activated macrophage cells. The results suggested that the inhibition of IKK activity by TF-3 and other tea polyphenols could occur by a direct effect on IKKs or on upstream events in the Signal transduction pathway. TF-3 and other tea polyphenols blocked phosphorylation of IB from the cytosolic fraction, inhibited NFB activity and inhibited increases in inducible nitric oxide synthase levels in activated macrophage. TF-3 and other tea polyphenols also inhibited strongly the activities of xanthine oxidase, cyclooxygenase, EGF-receptor tyrosine kinase and protein kinase C. These results suggest that TF-3 and other tea polyphenols may exert their cancer chemoprevention through suppressing tumor promotion and inflammation by blocking Signal transduction. The mechanisms of this inhibition may be due to the blockade of the mitogenic and differentiating Signals through Modulating EGFR function, MAPK cascades, NFkB activation as wll as c-myc, c-jun and c-fos expression.

  • Cancer chemoprevention by tea polyphenols through Modulating Signal transduction pathways.
    Archives of pharmacal research, 2002
    Co-Authors: Jenkun Lin
    Abstract:

    The action mechanisms of several chemopreventive agents derived from herbal medicine and edible plants have become attractive issues in cancer research. Tea is the most widely consumed beverage worldwide. Recently, the cancer chemopreventive actions of tea have been intensively investigated. It have been demonstrated that the active principles of tea were attributed to their tea polyphenols. Recently, tremendous progress has been made in elucidating the molecular mechanisms of cancer chemoprevention by tea and tea polyphenols. The suppression of various tumor biomarkers including growth factor receptor tyrosine kinases, cytokine receptor kinases, PI3K, phosphatases, ras, raf, MAPK cascades, N x FB, I x B kinase, PKA, PKB, PKC, c-jun, c-fos, c-myc, cdks, cyclins, and related transducing proteins by tea polyphenols has been studied in our laboratory and others. The I x B kinase (IKK) activity in LPS-activated murine macrophages (RAW 264.7 cells) was found to be inhibited by various tea polyphenols including (-) epigallocatechin-3-gallate (EGCG), theaflavin (TF-1), theaflavin-3-gallate (TF-2) and theaflavin-3,3'-digallate (TF-3). TF-3 inhibited IKK activity in activated macrophages more strongly than did the other tea polyphenols. TF-3 inhibited both IKK1 and IKK2 activity and prevented the degradation of I x B x and I x B x in activated macrophage cells. The results suggested that the inhibition of IKK activity by TF-3 and other tea polyphenols could occur by a direct effect on IKKs or on upstream events in the Signal transduction pathway. TF-3 and other tea polyphenols blocked phosphorylation of IB from the cytosolic fraction, inhibited NFB activity and inhibited increases in inducible nitric oxide synthase levels in activated macrophage. TF-3 and other tea polyphenols also inhibited strongly the activities of xanthine oxidase, cyclooxygenase, EGF-receptor tyrosine kinase and protein kinase C. These results suggest that TF-3 and other tea polyphenols may exert their cancer chemoprevention through suppressing tumor promotion and inflammation by blocking Signal transduction. The mechanisms of this inhibition may be due to the blockade of the mitogenic and differentiating Signals through Modulating EGFR function, MAPK cascades, NFkappaB activation as well as c-myc, c-jun and c-fos expression.

Akimichi Kaneko - One of the best experts on this subject based on the ideXlab platform.

Fusao Kawai - One of the best experts on this subject based on the ideXlab platform.

Rajashekar P. Mandi - One of the best experts on this subject based on the ideXlab platform.

  • Performance analysis of SPWM and SVPWM based three phase voltage source inverter
    Control theory & applications, 2016
    Co-Authors: K. Latha Shenoy, C. Gurudas Nayak, Rajashekar P. Mandi
    Abstract:

    Three phase voltage-fed PWM inverters are finding increased use in high power industrial drive applications. Various modulation techniques have been developed to obtain sinusoidal output with better harmonic quality. Among them, the space vector pulse width modulation technique provides low THD and larger under modulation range compared to sinusoidal pulse width modulation technique. A revolving reference vector is generated as voltage reference instead of three phase Modulating Signal in space vector based pulse width modulation technique

  • Performance Analysis of SPWM and SPWM and SVPWM Based Three Phase Voltage source Inverter
    2016
    Co-Authors: Latha K Shenoy, Gurudas C Nayak, Rajashekar P. Mandi
    Abstract:

    Three phase voltage-fed PWM inverters are finding increased use in high power industrial drive applications. Various modulation techniques have been developed to obtain sinusoidal output with better harmonic quality. Among them, the space vector pulse width modulation technique provides low THD and larger under modulation range compared to sinusoidal pulse width modulation technique. A revolving reference vector is generated as voltage reference instead of three phase Modulating Signal in space vector based pulse width modulation technique

Munagala Surya Kalavathi - One of the best experts on this subject based on the ideXlab platform.

  • Discontinuous PWM Technique for the Asymmetrical Dual Inverter Configuration to Eliminate the Overcharging of DC-Link Capacitor
    IEEE Transactions on Industrial Electronics, 2018
    Co-Authors: Maramreddy Harsha Vardhan Reddy, Teegala Bramhananda Reddy, Bumanapalli Ravindranath Reddy, Munagala Surya Kalavathi
    Abstract:

    To improve the quality of output voltage in the dual inverter fed open end winding induction motor drive, the dc voltages should be maintained in the ratio of 2:1. In such a configuration with a continuous Modulating Signal-based pulse width modulation (CPWM) technique, overcharging of the dc-link capacitor of inverter with low input dc voltage is observed (ratio of 2:1 is not maintained). Hence, wide range of speed control is not possible with the CPWM technique. The existing decoupled PWM methods and nested rectifier configuration may generate output voltage with poor quality and increase the cost of the drive system. This paper presents a discontinuous Modulating Signal-based PWM (DPWM) technique for asymmetrical dual inverter configuration, which eliminates the problem of overcharging of the dc-link. Hence, wide range of speed control is possible with better quality of output voltage. In the operating range, when compared to the CPWM technique, the DPWM technique reduces zero sequence voltage. The proposed PWM technique is easy to implement and does not require any reference voltage vector magnitude calculation, sector identification, and switching state selection as in space vector based PWM techniques. To show the effectiveness of the DPWM technique, experimental studies have been carried out, and results are presented and compared.