• Korean Journal of Weed Science
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• v.10 no.4
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• pp.255-260
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• 1990

Seventeen different herbicides were screened to select promising ones for the control of weeds, which may be used in paddy fields transplanted with 8 days old young rice seedlings. Four classes of herbicides were chosen and tested with seedlings grown under different cultivating conditions. Contact herbicides such as diphenyl-ether and oxadiazol showed severe growth retardation of rice seedlings. Carbamate class(dimepiperate), quinoline class (quinclorac), pyrazol class(pyrazolate), acid amide class(mefenacet and pretilachlor), addition of safener (pretilachlor+fenclorim and mefenacet+bensulfuron+dymuron) and unknown class (KC-7079) exhibited normal growth of seedlings. Sulfonyl urea herbicide class(cimosulfuron, bensulfuron, pyrazosulfuron), and oxarane class(tridiphane) showed the slight growth inhibition but recovered shortly.

• Journal of Microbiology and Biotechnology
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• v.33 no.3
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• pp.329-338
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• 2023

Enterohemorrhagic Escherichia coli (EHEC) is a foodborne pathogen that produces attaching and effacing lesions on the large intestine and causes hemorrhagic colitis. It is primarily transmitted through the consumption of contaminated meat or fresh produce. Similar to other bacterial pathogens, antibiotic resistance is of concern for EHEC. Furthermore, since the production of Shiga toxin by this pathogen is enhanced after antibiotic treatment, alternative agents that control EHEC are necessary. This study aimed to discover alternative treatments that target virulence factors and reduce EHEC toxicity. The locus of enterocyte effacement (LEE) is essential for EHEC attachment to host cells and virulence, and most of the LEE genes are positively regulated by the transcriptional regulator, Ler. GrlA protein, a transcriptional activator of ler, is thus a potential target for virulence inhibitors of EHEC. To identify the GrlA inhibitors, an in vivo high-throughput screening (HTS) system consisting of a GrlA-expressing plasmid and a reporter plasmid was constructed. Since the reporter luminescence gene was fused to the ler promoter, the bioluminescence would decrease if inhibitors affected the GrlA. By screening 8,201 compounds from the Korea Chemical Bank, we identified a novel GrlA inhibitor named Grlactin [3-[(2,4-dichlorophenoxy)methyl]-4-(3-methylbut-2-en-1-yl)-4,5-dihydro-1,2,4-oxadiazol-5-one], which suppresses the expression of LEE genes. Grlactin significantly diminished the adhesion of EHEC strain EDL933 to human epithelial cells without inhibiting bacterial growth. These findings suggest that the developed screening system was effective at identifying GrlA inhibitors, and Grlactin has potential for use as a novel anti-adhesion agent for EHEC while reducing the incidence of resistance.

• The Korean Journal of Physiology and Pharmacology
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• v.1 no.6
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• pp.783-796
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• 1997

The relaxation induced by stimulation of the inhibitory non-adrenergic, non-cholinergic (iNANC) nerve is mediated by the release of iNANC neurotransmitters such as nitric oxide (NO), vasoactive intestinal peptide (VIP) and adenosine triphosphate (ATP). The mechanisms of NO, VIP or ATP-induced relaxation have been partly determined in previous studies, but the detailed mechanism remains unknown. We tried to identify the nature of iNANC neurotransmitters in the smooth muscle of guinea pig ileum and to determine the mechanism of the inhibitory effect of nitric oxide. We measured the effect of NO-donors VIP and ATP on the intracellular $Ca^{2+}$ concentration$([Ca^{2+}]_i)$, by means of a fluorescence dye(fura 2) and tension simultaneously in the isolated guinea pig ileal smooth muscle. Following are the results obtained. 1. Sodium nitroprusside $(SNP:10^{-5}\;M)$ or S -nitro-N-acetyl-penicillamine $(SNP:10^{-5}\;M)$ decreased resting $[Ca^{2+}]_i$ I and tension of muscle. SNP or SNAP also inhibited rhythmic oscillation of $[Ca^{2+}]_i$ and tension. In 40mM $K^+$ solution or carbachol ($(CCh:10^{-6}\;M)$-induced precontracted muscle, SNP decreased muscle tension. VIP did not change $[Ca^{2+}]_i$ and tension in the resting or precontracted muscle, but ATP increased resting $[Ca^{2+}]_i$ and tension in the resting muscle. 2. 1H-[1,2,4]oxadiazol(4,3-a)quinoxalin-1-one $(ODQ:1\;{\mu}M)$, a specific inhibitor of soluble guanylate cyclase, limited the inhibitory effect of SNP 3. Glibenclamide $(10\;{\mu}M)$, a blocker of $K_{ATP}$ channel, and 4-aminopyridine (4-AP:5 mM), a blocker of delayed rectifier K channel, apamin $(0.1\;{\mu}M)$, a blocker of small conductance $K_{Ca}$ channel had no effect on the inhibitory effect of SNP. Iberiotoxin $(0.1\;{\mu}M)$, a blocker of large conductance $K_{Ca}$ channel, significantly increased the resting $[Ca^{2+}]_i$, and tension, and limited the inhibitory effect of SNP. 4. Nifedipine $(1\;{\mu}M)$ or elimination of external $Ca^{2+}$ decreased not only resting $[Ca^{2+}]_i$ and tension but also oscillation of $[Ca^{2+}]_i$ and tension. Ryanodine $(5\;{\mu}M)$ and cyclopiazonic acid $(10\;{\mu}M)$ decreased oscillation of $[Ca^{2+}]_i$ and tension. 5. SNP decreased $Ca^{2+}$ sensitivity of contractile protein. In conclusion, these results suggest that 1) NO is an inhibitory neurotransmitter in the guinea pig ileum, 2) the inhibitory effect of SNP on the $[Ca^{2+}]_i$ and tension of the muscle is due to a decrease in $[Ca^{2+}]_i$ by activation of the large conductance $K_{Ca}$ channel and a decrease in the sensitivity of contractile elements to $Ca^{2+}$ through activation of G-kinase.

• Korean Journal of Weed Science
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• v.14 no.1
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• pp.28-33
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• 1994

This study was conducted to investigate the efficacy of weed control by pyributicarb{O-[3-tert-butylphenyl] N-[6-methoxy-2-pyridyl]-N-methyl thiocarbamate}/bensulfuron-methyl{methyl 2-[[[[[[4, 6-dimethoxypyrimidin-2-yl] amino] carbonyl] amino] sulfonyl] methyl] benzoate} SC and oxadiazon{5-tert-butyl-3-[2,4-dichloro-5-isopropoxyphenyl]-1,3,4-oxadiazol-2(3)-one}/bensulfuron-methyl SC, and to develope weed control methods for paddy rice. There was little difference between suspension concentrate and granule of pyributicarb/bensulfuron-methyl and oxadiazon/bensulfuron-methyl combination in the effect of weed control. Pyributicarb/bensulfuron-methyl SC and oxadiazon/bensulfuron-methyl SC were diffused from the point of application to 6m. Pyributicarb/bensulfuron-methyl SC applied on water surface from irrigation inlet and in paddy water from dike controlled more than 90% of weeds. Pyributicarb/bensulfuron-methyl SC was precipitated about 1-2cm per 1 hour after dripping on water surface. The efficacy of weed control by pyributicarb/bensulfuron-methyl SC was higher in 0-1cm than in 6-7cm standing water depth.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.42 no.1
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• pp.79-88
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• 1997

This experiment was conducted to investigate the protoporphyrin Ⅸ (PPIX)accumulation, activity of antioxidative enzymes and contents of antioxidant in tolerant-wheat and susceptible-barley to protoporphyrinogen oxidase (Protox) inhibiting-herbicides [oxyfluorfen(2-chloro-l-(3-ethoxy-nitrophenoxy-4-(trifluoromethyl) benzene, acifluorfen (5-[2-chloro-4-(trifl-uoromethyl) phenoxy]-2-nitrobenzoic acid), bifenox(methyl-5-(2, 4-dichlorophenoxy) 2-nitroben-zoate), and oxadiazon (5-tert-butyl-3-(2,4-dichloro-5-isopropoxyphenyl)-1,3,4-oxadiazol-2-one)]. The tolerant-wheat and susceptible-barley were soaked in these compounds at 10$^{-6}$ M for 2hrs and exposed to light for 2,4,6 or 8hrs to investigate change of the activity of antioxidative enzymes. The activities of monodehydroascorbate reductase(MDAR), catalase(CAL) and superoxide dismutase(SOD) were lower in the barley than in the wheat after the treatement of these compounds. The activity of peroxidase(POX) was lower in the barley than in the wheat at 8hrs after the treatment of oxyfluorfen but other compounds showed no difference in activity in wheat and barley. The activity of glutathione reductase(GR) was increased in wheat and barley according as hours of treatment of these compounds became increased but its activity was no difference between wheat and barley. In the case of the content of vitamin C due to the treatment of these compounds, the wheat decreased less than the barley. After the treatment of oxyfluorfen the content of vitamin E in the wheat was higher than in the barley but other compounds didn't have any difference between wheat and barley. And after the treatment of acifluorfen the content of carotenoid was greater in the wheat than in the barley but other compounds didn't have any difference between wheat and barley. The content of glutathione (GSH, GSSG) was greater in the barley than in the wheat. The content of protoporphyrin Ⅸ (PPIX) accumulation by the treatments of these compounds was more in the barley than in the wheat. Especially, the treatment of oxyfluorfen and acifluorfen were more accumulated 2.3 and 1.3 fold in the barley than in the wheat, respectively.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.42 no.1
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• pp.68-78
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• 1997

Laboratory and greenhouse studies were conducted to determine differential sensitivities on absorption of $^{14}$ C-oxyfluorfen and the anatomical responses in wheat and barley to protoporphyrinogen oxidase-inhibiting herbicides [oxyfluorfen (2-chloro-1- (3-ethoxy -nitrophen-oxy)-4-(trifluoromethyl) benzene, acifluorfen(5-[2-chloro-4-(trifluoromethyl) phenoxy]-2-nitro-benzoic acid), bifenox(methyl-5-(2, 4-dichlorophenoxy)-2-nitrobenzoate) and oxadiazon(5-tert-butyl-3-(2, 4-dichloro-5-isopropoxyphenyl)-1, 3, 4-oxadiazol-2-one)]. I$_{50}$ value of the tolerant wheat cultivars to oxyfluorfen was about 10$^{-4}$ , whereas that of the susceptible barley cultivars was about 10$^{-6}$ M, showing significant difference between the two groups. When foliage were applied with acifluorfen, bifenox or oxadiazon, the oxyfluorfen-tolerant wheat showed less decreased in shoot fresh weight and chlorophyll content than the susceptible barley. Also, when soil-applied with these herbicides test plants showed similar tendency in foliar application. Electrolyte leakage from the tissue treated with these compounds was the more influenced in the barley than the wheat. Malondialdehyde(MDA) production as index of lipid peroxidation was greater in the barley than the wheat by treatment of these compounds. Therefore, the differential sensitivities of wheat and barley to protoporphyrinogen oxidaseinhibiting herbicides was showed by our greenhouse and in vitro experiment. The absorption rates of $^{14}$ C-oxyfluorfen were higher in the barley than the wheat. And this tendency was showed appararitly difference by increase of treatment durations. After the oxfluorfen and oxadiazon treatment, the tolerant wheat did not show the structural damage in leaf surface, but the susceptible barley was damaged in the leaf waxy layer. However, the acifluorfen and bifenox treatment showed no difference between wheat and barley. The anatomical changes by these compounds treatment were not observed in the tolerant wheat but epidermal cell and mesophyll cell were highly broken in the susceptible barley.

• Korean Journal of Weed Science
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• v.17 no.1
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• pp.31-43
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• 1997

This study was carried out to investigate classfication of weedy rice (Oryza sativa) based on isozymes esterase and peroxidase, growth and developmental difference of weedy rices and rices grown under dry and water condition, and weedy rice control and tolerant difference of weedy rices in various herbicides using weedy rices collected from thirteen strains of Chonnam, one Chonbuk, two Kyeongki and two rice cultivars. 1. The collected weedy rices were classified into three groups based on isozyme esterase and peroxidase using polyacrylamide gel electrophoresis(PAGE) method. The classified groups were not same each other. 2. Plant height was taller in collected weedy rices than rice cultivars at 18 days after seeding under dry and water conditions, but number of leaves, shoot fresh weight, root fresh weight and root length were not significantly different between collected weedy rices and rice cultivars. In addition, growths of collected weedy rices were greater in dry- than water-condition. 3. After thiobencarb(S-4-chlorobenzyl diethythiocarbamate), molinate(S-ethyl hexahydro-1H-azepine-1-carbothioate) and oxadiazon(5-tert-butyl-3(2,4-dichloro-5-isopropoxyphenyl)-1,3,4-oxadiazol-2-one) were applied at 6 days before seeding, the weedy rices controlled 100% by thiobencarb at 2.1kg ai/ha and 024kg ai/ha oxadiazon treatment but controlled 26% to 67% by molinate at 6.5kg ai/ha. Rice due to the herbicides was injured severely(25% to 100%) in flood condition at time of rice seeding after oxadiazon at 0.48kg ai/ha and 2.1kg ai/ha thiobencarb application, except for molinate which injured rice slightly(4% to 13%) in drain condition. The collected weedy rices to all experimented herbicides showed slight intraspecific variations. The intraspecific variations of weedy rices decreased in the order of thiobencarb>molinate>oxadiazon.