• Korean Journal of Environmental Agriculture
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• v.21 no.2
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• pp.149-155
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• 2002

Two pesticides commonly used for lettuce cultivation including chlorpyrifos and procymidone were subjected to a field residue trial to ensure safety of terminal residues in the harvest. After pesticides were applied at standard and double rates in a foliar spray, leaf persistence of their residues was investigated far 10 days prior to harvest. Even though far exceeded the tolerances, initial leaf residues were rapidly dissipated with time and remained only 0.4$\sim$7.2% of the residues in the harvest. As well fitted by the first-order kinetics, biological half-lives of the pesticide residues in lettuce leaves ranged 1.2$\sim$2.6 days. Slow dissipation of the residues in the harvest was observed during storage at room temperature and 4$^{\circ}C$ for 7 days. Portions of dislodgeable residues which resided in detergent washings decreased as time elapsed. Patterns in dissipation and distribution of dislodgeable residues were not largely affected by the application rate of pesticides. It is concluded that timing of pesticide application, that is, pre-harvest interval would be the first factor to determine the terminal residue level in edible portions of lettuce.

• Analytical Science and Technology
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• v.26 no.3
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• pp.174-181
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• 2013

Pyrifluquinazon is classified with a quinazoline insecticide that regulates food intake by controling the feeding behavior acting on the endocrine or nervous system of pests such as aphids and white fly. To keep safety on pyrifluquinazon residues in agricultural commodities a simple, accurate and rapid analytical method was developed and validated using high performance liquid chromatograph (HPLC-UVD). The pyrifluquinazon residues acidified with 1% formic acid in samples were extracted with acetonitrile and partitioned with hexane subsequently to dichloromethane then purified with silica solid phase extraction (SPE) cartridge. The purified samples were detected using HPLC-UVD. The method was validated using apple and pear spiked with pyrifluquinazon at 0.02, 0.05 and 0.1 mg/kg and hulled rice, pepper, soybean at 0.05 and 0.1 mg/kg. Average recoveries were 70.5~107.9% with relative standard deviation less than 10%. The result of recoveries and overall coefficient of variation of a laboratory results in Gwangju regional FDA and Daejeon regional FDA was followed with Codex guideline (CODEX CAC/GL 40). This method is appropriated at pyrifluquinazon residues determination and will be used as official method of analysis.

• Journal of Food Hygiene and Safety
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• v.29 no.4
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• pp.292-298
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• 2014

Tridemorph is a systemic morpholine fungicide for crops. The objective of this study was to develop reliable and sensitive analytical method for determination of tridemorph residues in tea samples for ensuring the food safety. Tridemorph residues in samples were extracted with acetonitrile after hydration, partitioned with saline water, and then purified using an aminopropyl ($NH_2$) SPE cartridge. The purified samples were detected and quantified using LC-ESI-MS/MS. The linear detection limits for tridemorph ranged from 0.02 to $1.0mgL^{-1}$ with a correlation coefficient of 0.9999. The method was validated using tea samples spiked with tridemorph at different concentration levels (0.02 and $0.05{\mu}gmL^{-1}$). The average recovery ranged between 75.0 and 84.7% with relative standard deviations less than 10%. The LOD and LOQ were 0.01 and $0.02mgL^{-1}$, respectively. The developed method was applied successfully to the identification of tridemorph in real tea samples obtained from different sources, and tridemorph was not detected in any of the samples. The results show that the developed analytical method is accurate and suitable for tridemorph determination in tea samples.

• BMB Reports
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• v.32 no.6
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• pp.547-553
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• 1999

Aminoacyl-tRNA synthetases are essential enzymes catalyzing the attachment of specific amino acids to cognate tRNAs. In the present work, the substrate analogue L-methionine hydroxamate was used to identify functional residues located in the active site of the E. coli methionyl-tRNA synthetase (MetRS). This compound inhibited bacteria, yeast, and human MetRS activities to a similar degree, suggesting a conserved active site structure and mechanism between MetRSs of different phylogenetic domains. Mutants of the E. coli MetRS resistant to methionine hydroxamate were also isolated. These mutants contained a substitution either at T10, Y15, or Y94. These residues are highly conserved among the different MetRSs and the mutants showed decreased aminoacylation activity, suggesting their functional and structural significances. The putative roles of these residues are discussed on a structural basis.

• Korean Journal of Microbiology
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• v.29 no.2
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• pp.136-142
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• 1991

The selection of ethanol-tolerant strains was applied to enrichment culture of YPD broth medium containing various concentrations of ethanol. Isolates were identified to be Saccharomyces cerevisiae, the others as S. dairensis, S. exiguus, S. telluris, Saccharomycodes ludwigii, Schwanniomyces occidentalis var. occidentalis and Zygosaccharomyces florentinus. Among isolates S. cerevisiae YO-1 was screened as having the highest ethanol tolerance and produced 18% (v/v) ethanol after 4 days fermentation. The change of fatty-acyl residues represents that a progressive decrease in fatty-acyl unsaturation and a proportional increase in saturation in phospholipids of yeast cells during fermentation affected the yeast viability. Supplementation ethanol to the cultures led to an increase of unsaturated fatty-acyl residues, especially $C_{16}$ or $C_{18}$ residues, along with a decrease in the proportion of saturated residues in cellular phospholipids. Increasing the amount of soy flour led to an increase in the maximum number of viable yeast cells and ethanol production. It was possible in 4 days to reach 21% (v/v) ethanol by adding 4% soy flour as source of unsaturated fatty-acyl residues to the fermentation medium. Soy flour not only increased yeast population but also enhanced the physiological properties of yeast cells to be ethanol tolerant in the anaerobic culture.

• The Korean Journal of Physiology and Pharmacology
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• v.22 no.1
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• pp.91-99
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• 2018

Protein phosphatase 1 (PP1) is involved in various signal transduction mechanisms as an extensive regulator. The PP1 catalytic subunit (PP1c) recognizes and binds to PP1-binding consensus residues (FxxR/KxR/K) in NBCe1-B. Consequently, we focused on identifying the function of the PP1-binding consensus residue, $^{922}FMDRLK^{927}$, in NBCe1-B. Using site-directed mutagenesis and co-immunoprecipitation assays, we revealed that in cases where the residues were substituted (F922A, R925A, and K927A) or deleted (deletion of amino acids 922-927), NBCe1-B mutants inhibited PP1 binding to NBCe1-B. Additionally, by recording the intracellular pH, we found that PP1-binding consensus residues in NBCe1-B were not only critical for NBCe1-B activity, but also relevant to its surface expression level. Therefore, we reported that NBCe1-B, as a substrate of PP1, contains these residues in the C-terminal region and that the direct interaction between NBCe1-B and PP1 is functionally critical in controlling the regulation of the ${HCO_3}^-$ transport. These results suggested that like IRBIT, PP1 was another novel regulator of ${HCO_3}^-$ secretion in several types of epithelia.

• Korean Journal of Veterinary Service
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• v.15 no.2
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• pp.93-100
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• 1992

The purpose of the present survey was to evaluate the antibiotic residues in meats and internal organs such as muscle, liver, heart, kidney and spleen of cattle (n=59) and pigs (n=115). The EEC-4-plate-method were employed. The results were obtained as follows ; 1. In BS 6.0, BS 7.2 and BS 8.0 used as media to detect antibiotic residues, the zone($M{\pm}SD,$ cm) of bacterial growth inhibition was narrow($1.40{\pm}0$) in meats, whereas the zone was wide($1.69{\pm}0.25-1.88{\pm}0.23$ and $1.58{\pm}0.18-1.86{\pm}0.15$ in cattle and pigs, respectively) in internal organs. But in SL 8.0, it was difficult to detect the zones ($0-1.40{\pm}0$) of both meats and internal organs. 2. Residues of antibiotic in beef and pork were rarely detected in BS 6.0, BS 7.2 and BS 8.0 (range 1.7-11.9% and 2.6-4.3%, respectively), whereas residual percentages of internal organs were relatively higher(range 69.5-96.6% and 43.5-84.3%, respectively). But in SL 8.0, it was not detected in both beef or pork, whereas they were 0-13.6% and 0-4.3% in interanal organs.

• Journal of Dairy Science and Biotechnology
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• v.31 no.1
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• pp.59-65
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• 2013

Antibiotic residues are undesirable in milk and milk products for a number of reasons. In particular, they can have harmful effects on public health and harm to the manufacturer of the cultured milk products, e.g. MRSA etc. Although government regulatory agencies and the dairy industry have been successful in decreasing the presence of high concentrations of antibiotic residues, violations still occur and lead to contaminated products. As a result, several rapid and reliable methods for the detection of antibiotic residues have been developed, including microbiological and instrumental analysis methods. The conventional methods are time consuming, but recent improvements have allowed for better detection time, sensitivity, and accuracy. An example of an advanced detection instrument is the biosensor, which has several applications in food and environmental science, e.g. food-born pathogen detection, antimicrobial residues etc. In the present review, the recent trends in the methods used to test for antibiotic residues in milk and dairy products, as well as their specific applications, have been discussed.

• Asian-Australasian Journal of Animal Sciences
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• v.17 no.7
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• pp.967-972
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• 2004

Four Holstein$\times$Indigenous cows with ruminal canulas were used in a 4$\times$4 Latin square design with 28 d periods to determine the effect of replacing nonforage fiber source (NFFS) from cassava residues for non-fiber carbohydrates (NFC) on ruminal fermentation characteristics and milk production. Dietary treatments contained 17% forage neutral detergent fiber (FNDF) from corn silage and 0, 3, 6 and 9% nonforage NDF from cassava residues and 11% nonforage NDF from other NFFS, so that levels of nonforage NDF were 11, 14, 17 and 20% dry matter (DM). Intakes of DM and net energy for lactation, average daily gain and milk fat percentage were not different (p>0.05). Ruminal pH, ammonia concentrations, acetate to propionate ratios, 24 h in sacco fiber digestibility significantly increased with increasing contents of nonforage NDF from cassava residues. Concentrations of VFA, urinary excretion of purine derivatives, milk protein percentage, production of milk and 4% FCM significantly decreased. These results suggest that NFC in diets is one of the limiting factors affecting productivity of dairy cows in the tropics and thus NFFS is better used as partial replacements for FNDF.

• Korean Journal of Veterinary Service
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• v.28 no.3
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• pp.285-294
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• 2005

This study was conducted to investigate the extraction method for the determination of organochlorine, organophosphorus and synthetic pyrethroid pesticide residues in beef fat by gas chromatography-mass selective detector(GC-MSD). Twenty one pesticide residues in fat were determined using a simple and rapid procedure based on solid- phase extraction(SPE) clean-up cartridges with octadecyl $(C_{18})-bonded$ porous silica, florisil, $10\%$ deactivated florisil. a tandem $C_{18}$ and florisil and a tandem $C_{18}$ and $10\%$ deactivated florisil. Solvent-solvent extraction using acetonitrile was not satisfied to eliminate fat interference for pesticide residue analysis by GC-MSD, and the recoveries of the method in fat ranged from 16.2 to $57.3\%$ except DDT$(83.2\%)$. The recoveries of SPE methods using a tandem $C_{18}$ and Florisil was $59.6\~123.8\%$ except fenitrothion $(135.2\%)$. the SPE method was verified the satisfactory performance of pre-treatment for pesticide residues analysis in fat by GC-MSD. The efficiency of florisil deactivated with $10\%$ water has been not proved significantly on recoveries of pesticide residues in fat.