• Environmental Mutagens and Carcinogens
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• v.15 no.2
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• pp.88-93
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• 1995

Effects of hyperthermia on the induction of DNA single strand breaks and replication inhibition were studied in bleomycin-treated CHO-K$_1$ cells by alkaline elution and alkaline sucrose gradient sedimentation. Bleomycin-induced DNA single strand breaks of DNA were dose-and time-dependently increased, and these strand breaks of DNA were gradually rejoined as post-incubation time passed. Treatment with hyperthermia alone did not affect the induction of DNA single strand breaks. However, pre-exposure of cells to hyperthermia followed by bleomycin treatment greatly increased the single strand breaks, and also reduced the rejoining processes of bleomycin-induced DNA single strand breaks. Bleomycin selectively inhibited the replicon initiation. The combined treatment with hyperthermia and bleomycin markedly potentiated the nonspecific inhibition of replication.

• Journal of Environmental Health Sciences
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• v.19 no.3
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• pp.64-73
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• 1993

The study was conducted to investigate the mechanism of tumor promotion as the time courses and the doses of promoter, and the effect of plant fiavonoids on the TPA-induced ODC responses. The results are summarized as follows: 1. A single, toppical application of 17 nmole of the potent tumor promoter, 12-O-tetradecanoyl phorbol-13-acetate, resulted in an induction of mouse epidermal Ornithine Decarboxylase with a peak at 5 hours after treatment and maximized 5.1 times as large as ODC activities of control. 2. Dose-response curve indicated that the tumor promotion increases proportionally between 1.7 and 170 nmole of TPA. This dose dependency relationship indicated that the ability of TPA to stimulate ODC is linked its ability to promote tumors. 3. Naturally occurring plant fiavonoids with anticarcinogenic and antipromotional activities were tested for their abilities to inhibit ODC response induced by skin tumor promoter TPA. Intra peritoneal administration of fiavonoids compounds (rutin, naphthofiavone, baicalein, quercitrin) and herbal drugs (sophorae rios, crataegi fructus, armeniacae semen) inhibited 17 nmole TPA-induced ODC activities in mouse epidermis in vivo.

• Toxicological Research
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• v.17
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• pp.251-256
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• 2001

The expression of phase II detoxifying enzymes is affected by a variety of compounds and the induction of the enzymes plays an essential role in chemoprevention. A variety of phytochemicals such as sulfur-containing chemoprotective agents (SCC) may trigger cellular signals and activate phase II gene expression through ARE activation. see induces glutathione S-transferases. Studies were conducted to investigate the role of mitogen-activated protein (MAP) kinase and phosphatidylinositol 3-kinase (PI3-kinase) in the induction of GST (e.g. rGSTA2) by sec. We also studied the MAP kinase pathway responsible for the GST expression by see and compared that with the pathway activated by oxidative stress as a result of sulfur amino acids deprivation (SAAD). see inhibited phosphorylation of ERK1/2 although the effect of see on JNK and p38 MAP kinase was minimal. Wortmannin and LY294002. PI3-kinase inhibitors. abolished the increases in rGSTA2 mRNA and protein levels by SCC. Deprivation of cystine and methionine caused oxidative stress in H4IIE cells. as evidenced by a decrease in the reduced glutathione and an increase in prooxidant production. Electrophoretic mobility shift assay revealed that the ARE complex consisting of Nrf-1/2 and Maf proteins was activated 12~48 h. The rGSTA2 mRNA and protein levels were increased by SAAD. Activation of ARE and induction of rGSTA2 were both completely inhibited by PI3-kinase inhibitors. Inhibition of p38 MAP kinase by SB203580 prevented the ARE-mediated rGSTA2 induction. The results of this study showed that PI3-kinase might play an essential role in the ARE-mediated rGSTA2 induction by see or SAAD and that the dual MAP kinase pathways were responsible for the enzyme induction.

• Korean Journal of Environmental Biology
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• v.18 no.1
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• pp.47-51
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• 2000

Phytophthora blight of pepper, which is caused by Phytophthora capsici Leonian, is not only the most destructive disease worldwide, but also difficult to control effectively. It has been needed to have new trials for effective control to the disease. We employed radiation hormesis of gamma ray as the new trial in the control strategy. Two cultivars, Kwangbok and Dabok, were used to analyse whether gamma ray radiation can induce disease resistance. The germination rate of pepper seeds was significantly enhanced by the radiation at all dose levels. Stimulatory effect for resistance induction was found to differ between cultivars. It was confirmed that the remarkable effect was induced in Dabok and depended on radiation dosage. Disease resistance at 4 Gy was much higher than that of control. On the other hand, no detectable induction effect for resistance was observed in Kwangbok which was moderate resistant cultivar to gamma ray radiation. [Hormesis, Gamma ray, Pepper, Phytophthora blight, Resistance induction].

• Environmental Analysis Health and Toxicology
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• v.13 no.3_4
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• pp.55-61
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• 1998

Glutathione-S-transferases (GSTs) detoxify electrophilic xenobiotics and reactive metabolites. Recently benzene-fused heterocycles have been shown to increase the total amount of hepatic GSTs in rats. Primarily this study aimed to determine the induction of GSTs by benzoazoles (BAs) including benzoxazole (BX), 2-methylbenzoxazole (M-BX), 2,5-dimethyl benzoxazole (D-BX), benzothiazole (BT), aminobenzothiazole (A-BT) and 2-mercaptobenzothiazole (M-BT) in rats. Hepatic cytosol and poly(A)$^+$ mRNA were prepared from rats after oral administration of BX, BT, M-BX, D-BX, A-BT and M-BT for 5 consecutive days at doses of 1 mmol/kg. Western immunoblot and northern blot analysis were conducted with rabbit anti-GST Ya, Yb$_1$, Yb$_2$, Yc antibodies and cDNA probes containing = 500 bps in the specific coding regions of Ya, Yb$_1$, Yb$_2$, Yc$_1$, and Yc$_2$, respectively. All BAs increased the amount of enzymes and mRNA levels of GSTs. BT was the most effective inducer of GSTs among the compounds examined in this study. Although A-BT and M-BT, the derivatives of BT, induced GSTs, these chemicals had lesser effect on induction of GSTs than BT. The derivatives of BX also induced less GSTs than the parent compound and the addition of methyl group to the benzene ring of BX reduced the induction of GSTs. BAs had better inductive effects on the class $\alpha$(Ya, Yc) than class $\mu$ GSTs (Yb$_1$, Yb$_2$). BAs enhanced mRNA levels of GSTs in parallel with the protein levels. These results indicate that 1) most of BAs induced various isozymes of GSTs, 2) the induction of GSTs appears to be correlated with the chemical structure of the derivatives, and 3) the expression of GST by BAs is presumably under the transcriptional regulation.

• Toxicological Research
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• v.15 no.1
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• pp.89-93
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• 1999

2,3,7,8-Tetrachlorodibenzo-p-dioxin(TCDD) is known to induce cytochrome p450 1A1 and to activate c-Src kinase and p21 Ras. This study examined the molecular interactions of adaptor proteins including Shc, Grb2, and Sos in rat primary hepatocytes and their relationship to the induction of CYP1A1 by TCDD. TCDD induced CYP1A1 level and EROD activity in a dose-dependent mode. Sos/Grb2 association isincreased by TCDDㅑㅜ a dose dependent mode. Tyrosine phosphorylated Shc, mainly p152, onloads to Grb2/Sos complex upon TCDD stimulation. The electrophoretic mobility shift of Sos is showed by TCDD. These results indicate that TCDD modulated the molecular interaction features of adaptor compoes proteins including Shc, Grb2, and Cnl in early signaling pathway of TCDD-mediated CYP 1A1 induction of rat primary hepatocyte.

• Toxicological Research
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• v.19 no.1
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• pp.33-37
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• 2003

Asiaticoside has been tested for the ability as an anti-inflammatory drug using lipopolysaccharide (LPS)-stimulated macrophage cell line (RAW 264.7 cell). LPS treatment induced dramatically inducible nitric oxide synthase (iNOS) in RAW cells. However, asiaticoside inhibited LPS-stimulated iNOS induction in a concentration-dependent manner. Especially, higher concentrations (＞50 $\mu\textrm{M}$) of asiaticoside completely blocked iNOS induction. In addition, LPS-stimulated expression of inducible cyclooxygenase (COX-2) and interleukin-1 $\alpha$ (IL-1 $\alpha$) was inhibited by asiaticoside treatment. Asiaticoside up to 50 $\mu\textrm{M}$ still required to inhibit COX-2 and IL-1 $\alpha$ induced by LPS. Consistent with these findings, treatment with asiaticoside suppressed do novo synthesis and cellular accumulation of prostaglandin $E_2$ to a lesser extent, suggesting that asiaticoside blocked the induction as well as the activity of COX-2 These results suggest the possibility that asiaticoside may be effective therapeutic agents for septic shock and other inflammatory diseases.

• Proceedings of the Korean Society of Toxicology Conference
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• 2003.05a
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• pp.72-72
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• 2003

Induction of glutathione S-transferases is associated with cancer chemoprevention. We reported that PD98059, an MKK1 inhibitor, induces glutathione Stransferase A2 (rGSTA2). This report comparatively examines the role of CCAAT/enhancer binding protein (C/EBP) and Nrf-2 in the induction of rGSTA2 by PD98059. PD98059 at the concentrations effective for the inhibition of MKKI increased the rGSTA2 protein and mRNA levels in H4IIE cells. (omitted)

• Proceedings of the KIPE Conference
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• 2003.11a
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• pp.123-126
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• 2003

This paper proposes a speed-sensorless induction motor control system using the rotor flux error. The rotor flux observer uses the reduced- dimensional state estimator technique instead of directly measuring the rotor flux. The estimated rotor speed is obtained directly from the electrical frequency, the slip frequency, and the rotor speed compensation with the estimated q-axis rotor flux. To precisely estimate the rotor flux, the actual value of the stator resistance, whose actual variation is reflected, is derived. For fast calculation and improved performance of the proposed algorithm, all control functions are implemented in software using a digital signal processor (DSP) with its environmental circuits. Also, it is shown through experimental results that the proposed system gives good performance for the speed-sensorless induction motor control.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2003.04a
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• pp.340-343
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• 2003

Soils contaminated by hazardous hydrophobic organic compounds, such as polycyclic aromatic hydrocarbons (PAHs), have become a major environmental issue due to toxic and carcinogenic properties of those compounds. In this work, we investigated effects of various metabolic inducers on phenanthrene biodegradation. Biodegradation tests were peformed with two different Pseudomonads: Pseudononrdia hydrocarboxydans (Gram positive) and Pseudomonas putida (Gram negative). Intermediates of phenanthrene metabolism (1-hydroxy-2-naphthoate, salicylate, catechol, phthalate and protocatechuate) were selected as inducers. The tests indicated that 1-hydroxy-2-naphthoate was the most effective inducer and enhanced the phenanthrene degradation rate up to 5.7 times, even though all the others also had induction ability to some extent. The effective induction could be achieved even at a low concentration of 1-hydroxy-2-naphthoate. Addition of metabolic inducers would be an attractive trick for the successful bioremediation of PAH-contaminated soil.