• Journal of Microbiology and Biotechnology
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• v.20 no.4
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• pp.678-682
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• 2010

The deletion of sti from the Streptomyces plasmid pIJ101 made its derivative pHZ1358 an efficient vector for gene disruption and replacement. Here, pHZ1358 was further optimized by the construction of a derivative plasmid pJTU1278, in which a cassette carrying multiple cloning sites and a lacZ selection marker were introduced for convenient plasmid construction in E. coli. In addition, the oriT region of pJTU1278 was also deleted, generating a vector (pJTU1289) that can be used specifically for PCR-targeting. The efficient usage of these vectors was demonstrated by the deletion of the gene involved in avermectin biosynthesis in S. avermitilis.

• Korean Journal of Veterinary Research
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• v.37 no.4
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• pp.855-862
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• 1997

Ivermectin is a synthetic derivative of the naturally occurring avermectin $B_{1a}$ (22, 23-dihydroavermectin $B_{1a}$) and $B_{1b}$ (22, 23-dihydroavermectin $B_{1b}$), It is widely used as antiparasitic and pesticidal agents because of its remarkably potent and broad spectrum of antiparasitic activity. Although the drug has shown excellent anthelmintic effects, development of toxicosis in some animals such as the Collie species of dog is well documented. However, no studies have been reported on the toxic effects of the drug in Korean native animals such as the Jindo dog. The toxic effect of ivermectin was evaluated in 25 Jindo dogs divided into five groups which were orally administered with ivermectin at dosage levels of $200{\mu}g/kg$, $300{\mu}g/kg$, $600{\mu}g/kg$ and $2,500{\mu}g/kg$ of body weight, respectively. Toxic signs were not observed in the groups receiving $200{\mu}g/kg$ and $300{\mu}g/kg$ B.W. ivermectin. One dog developed mild clinical signs of toxicosis in the group receiving $600{\mu}g/kg$ dosage of ivermectin. In the group with $2,500{\mu}g/kg$ dosage, all dogs developed mild (salivation, drooling, vomiting, mydriasis, and/or confusion) and/or moderate (ataxia and tremors) clinical signs of toxicosis. Hematologic changes were not observed in the groups receiving $200{\mu}g/kg$, $300{\mu}g/kg$ and $600{\mu}g/kg$ B.W. ivermectin. In the groups receiving $2,500{\mu}g/kg$ B.W., total erythrocyte counts, total and differential leukocyte counts and hemoglobin levels were not affected by drug. Aspartate aminotransferase levels were increased after administration of ivermectin, while serum cholesterol and blood glucose levels were decreased.

• Korean Journal of Environmental Agriculture
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• v.25 no.4
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• pp.359-364
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• 2006

Reversed-phase high-performance liquid chromatography (HPLC) techniques were developed to quantify abamectin (ABM) in paprika (Capsicum annum). Separation was achieved on a $C_{18}$ ODS column with a mobile phase of acetonitrile/water (96/4, v/v) mixture in an isocratic elution at the flow tate of 1.2 mL/min for avermectins (AVMs). The retention times were 8.0 and 9.7mins for AVM $B_{lb}$ and AVM $B_{1a}$, respectively. Residual AVMs (sum of AVM $B_{1a}$, AVM $B_{1b}$ and 8,9-Z-AVM $B_{1a}$) in the vegetable were extracted with acetonitrile, and the silica solid-phase extraction cartridges were used to purify the extract. AVMs were derivatized using trifluoroacetic acid and 1-methylimidazole, and the derivatives were determined with a fluorescence detector (excitation at 365 nm and emission at 470 nm). High and consistent recoveries, ranging from 93% to 115%, were obtained for AVM $B_{1a}$ and 8, 9-Z-AVM $B_{1a}$ at fortified levels of $20{\mu}g/kg\;and\;200{\mu}g/kg$ for paprika. The limit of quantitation (LOQ) was $2{\mu}g/kg$. The residual levels of AVMs in paprika in a field experiment from one day to seven days after the last application decreased from 18.40 to $7.59{\mu}g/kg$. The half-life $(T_{1/2})$ of AVMs in paprika was 1.47 days.

• KSBB Journal
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• v.16 no.5
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• pp.516-522
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• 2001

The large-scale production of antibiotics by filamentous mycelial organism requires and adequate supply of dissolved oxygen. In terms of productivity, it means that oxygen transfer is the rate-limiting step. Therefore, the oxygen transfer coefficients(K$\_$L/A) were determined in a broth involving a filamentous mycelial organism such as Streptomyces avermitilis for use in fermentations. To determine (K$\_$L/A) inn a stirred vessel, a great deal of effort is required to provide all the cells with a sufficient oxygen supply. To overcome the oxygen limitation in a batch culture, a fed-batch culture was applied to control the growth rate by an intermittent supply of nutrients. Thus, it was possible to maintain a suitable dissolved oxygen concentration at a low agitation rate. The optimal agitation speed was 350 rpm at low cell concentrations (below 7 g/L) by considering the efficiency of agitation and shear stress. The (K$\_$L/A) was found to decrease from 64.26 to 29.21h.$\^$-1/ when the biomass concentration was increased from 9.82 to 12.06 g/L. In addition, and increase in viscosity was also observed during the growth phase. By comparing the (K$\_$L/A) values for the various agitation and aeration rates, it was found that the effect of an increase in (K$\_$L/A) by aeration was reduced dramatically at high biomass concentrations. However, this effect was not observed when altering the agitation rate. This suggests that controlling the dissolved oxygen concentration by altering the agitation rate was more efficient than increase the aeration rate.

• Korean journal of applied entomology
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• v.47 no.1
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• pp.45-50
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• 2008

For the development of friendly environmental control of the beet armyworm, Spodoptera exigua that is too hard to control in the field, 25 insecticides were chosen from 58 registered to the beet armyworm, and bioassayed. There are 12 insecticides with neurotoxical activities, 10 with insect growth regulators and 3 Bacillus thuringiensis products. Among 12 insecticides with neurotoxical activities, mortality of S. exigua was 100% with emamectin benzoate (EC) and indoxacarb (WP) within 3 and 5 days after application, respectively. Otherwise, WG and SC of indoxacarb, Indoxacarb + etofenprox (WP) and pyridalyl (EW) were showed up to 91 %. Methoxyfenozide + spinosad (SC) was better than any other insect growth regulator as 100% mortality within 3 days after application. And methoxyfenozide (WP), tebufenozide (WP) and methoxyfenozide (SC) were 92% by 5 days. However, 3 kinds of B. thuringiensis products were showed under 35% mortality within 5 days from first spray.

• Korean journal of applied entomology
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• v.59 no.1
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• pp.5-13
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• 2020

Cockroaches are a not only nuisance insects but also have medical importance as they mechanically propagate various pathogens. To date, baits have been widely suggested for use in cockroach control. In this study, we investigated the insecticidal effects of three Korean baits-Korea Combat Ultra Slim (K-CUS), Korea Combat Power (K-CP), and Korea Zaps Dual Bait (K-ZDB)-and three US baits-US Combat Source Kill Max (US-CSKM), US Hot Shot MaxAttrax Roach Bait (US-HSM), and US Raid Double Control Small Roach Bait (US-RDC)-on the German cockroach (Blattella germanica). Among the six baits, three (K-CUS, K-CP, and US-CSKM), the main active ingredients of fipronil, showed rapid and strong insecticidal efficacy. In addition, we compared the persistence of the insecticidal effects of K-CUS and K-CP 6 months and 12 months after initial opening. Insecticidal effects of both baits decreased over time, but the mortality rates of cockroaches exposed to 6-month- and 12-month-aged baits were over 90%, suggesting that these baits can maintain their insecticidal effect for at least one year after indoor installation.