• Korean Journal of Veterinary Research
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• v.39 no.4
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• pp.765-771
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• 1999

Unlike most Escherichia coli strains, E coli O157 : H7 didn't ferment sorbitol within 24h of incubation and showed a negative reaction for $\beta$-glucuronidase. We developed a new medium for the rapid isolation of E coli O157 : H7 using sorbitol MacConkey agar with cefixime, potassium tellurite and 4-methylumbelliferyl-${\beta}$-D-glucuronide (MUG) as a primary plating medium. The addition of $20{\mu}g/ml$ of vancomycin in enrichment broth for E coli O157 : H7 inhibited lots of Gram positive bacteria. Three strains (10.3%) of 29 non-O157 E coli strains and 3 strains (8.3%) of 36 Salmonella spp were inhibited at the $0.05{\mu}g/ml$ of cefixime and 23 strains (79.3%) of 29 non-O157 E coli strains and 12 strains (33.3%) of 36 Salmonella spp were inhibited at the $2.0{\mu}g/ml$ of potassium tellurite. But none of the E coli O157 : H7 was affected at these concentration. The addition of MUG at $100{\mu}g/ml$ level to sorbitol MacConkey agar with cefixime and potassium tellurite (CTM-SMAC) aided in the rapid isolation of E coli O157 : H7 from samples by checking sorbitol-negative and $\beta$-glucuronidase negative phenotypes simultaneously. In conclusion, inoculation of a positive in the O157 screening test from enrichment broth on CTM-SMAC appeared to be a rapid, cost-effective and sensitive method for the isolation of E coli O157 : H7.

• Development and Reproduction
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• v.25 no.4
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• pp.199-211
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• 2021

Equine chorionic gonadotropin (eCG), produced by the endometrial cups of the placenta after the first trimester, is a specific glycoprotein that displays dual luteinizing hormone (LH)-like and follicle-stimulating hormone (FSH)-like effects in non-equid species. However, in equidaes, eCG exhibits only LH-like activity. To identify the specific biological functions of glycosylated sites in eCG, we constructed the following site mutants of N- and O-linked glycosylation: eCGβ/αΔ56, substitution of α-subunit⁵⁶ N-linked glycosylation site; eCGβ-D/α, deletion of the O-linked glycosylation sites at the β-subunit, and eCGβ-D/αΔ56, double mutant. We produced recombinant eCG (rec-eCG) proteins in Chinese hamster ovary suspension (CHO-S) cells. We examined the biological activity of rec-eCG proteins in CHO-K1 cells expressing the eLH/CG receptor and found that signal transduction activities of deglycosylated mutants remarkably decreased. The EC₅₀ levels of eCGβ/αΔ56, eCGβ-D/α, and eCGβ-D/αΔ56 mutants decreased by 2.1-, 5.6-, and 3.4-fold, respectively, compared to that of wild-type eCG. The Rmax values of the mutants were 56%-80% those of wild-type eCG (141.9 nmol/10⁴ cells). Our results indicate that the biological activity of eCG is greatly affected by the removal of N- and O-linked glycosylation sites in cells expressing eLH/CGR. These results provide important information on rec-eCG in the regulation of specific glycosylation sites and improve our understanding of the specific biological activity of rec-eCG glycosylation sites in equidaes.

• Korean Journal of Food Science and Technology
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• v.29 no.5
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• pp.1016-1020
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• 1997

Treatments of irradiation alone and/or in combination with heat were investigated for the sterilization of Escherichia coli O157: H7. D values of the strain were 129.2 min at $50^{\circ}C$, 27.1 min at $55^{\circ}C$, and 2.4 min at $60^{\circ}C$. The survival effect of E. coli O157:H7 during heating at various media was investigated. On heating at temperature of $60^{\circ}C$ for 10 min, the strain was generally more resistant in the media containg such chemical substrates such as 0.03 M cysteine, 1% sodium citrate or 5% sucrose, whereas this strain was appeared weaker in the chemical substrates added group such as 1% meat extract, 1% casein or 1% casamino acid. In the case of irradiation alone, $D_{10}$ value of E. coli O157:H7 was 0.116 kGy, and inactivation factors were $17{\sim}25$ at doses of 2 to 3 kGy. Pre-and post-irradiation heating showed the same $D_{10}$ value about 0.07 kGy. And Inactivation factors were $25{\sim}41$ at doses of 2 to 3 kGy. Therefore, combination treatment with heat and irradiation significantly increased in inactivation rate by increasing radiation sensitivity of E. coli O157:H7.

• Journal of Sensor Science and Technology
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• v.32 no.4
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• pp.238-245
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• 2023

0.75(Bi_1/2Na_1/2)TiO₃-0.25SrTiO₃ (BNT-25ST) ceramics with high densities were successfully prepared at a sintering temperature of 1,000℃ by adding a mixture of 1 mol% CuO and 0.5 mol% Na₂CO₃ or 0.5 mol% CuO and 0.25 mol% Na₂CO₃. Double polarization-electric field (P-E) hysteresis curves and sprout-shaped bipolar strain-electric field (S-E) hysteresis curves with small negative strains were observed in the pristine and CuO-added BNT-25ST ceramics whereas the Na₂CO₃-added sample showed similar P-E and S-E curves to a typical ferroelectric. The pristine BNT-25ST ceramics showed an extremely large strain and a large-signal piezoelectric strain constant (d₃₃^*): 0.287 % at 80 kV/cm and 850 pm/V at 20 kV/cm. Similar values, 0.248 % at 80 kV/cm and 655 pm/V at 20 kV/cm, were obtained in the CuO-added sample. However, the pristine and CuO-added samples showed large hysteresis in unipolar S-E curves at an electric field of less than 20 kV/cm. The Na₂CO₃-added sample showed smaller values of the strain and d₃₃^* but displayed a linear change and small hysteresis in the unipolar S-E curve. The co-added sample with CuO and Na₂CO₃ displayed intermediate P-E and S-E hysteresis curves.

• Food Science and Biotechnology
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• v.16 no.2
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• pp.265-269
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• 2007

There is significant interest in finding new sources of acetylcholinesterase (AChE) inhibitors for use in treating Alzheimer's disease, since only a few AChE inhibitors are available for clinical use, such as galanthamine, physostigmine, and tacrine. The ethanol extract of Chrysanthemum indicum Linne flowers was analyzed and found to markedly decrease AChE activity. Acaciin and $acacetin-7-O-{\beta}-D-galactopyranoside$ were identified as the active compounds responsible for the AChE inhibition by using an activity-guided fractionation strategy. The relationship between structure and activity for five flavonoids (acaciin, $acacetin-7-O-{\beta}-D-galactopyranoside$, luteolin, and two other commercially available flavonoids, i.e., apigenin and acacetin) was also investigated, revealing that the presence of methoxy groups at C-4' in the B ring and a sugar at O-7 in ring A appear to be essential for the inhibition of AChE.

• Korean Journal of Food Science and Technology
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• v.30 no.5
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• pp.1209-1213
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• 1998

The gamma-radiation sensitivity of four kinds of Escherichia coli O157:H7 was investigated in frozen cells $(-18^{\circ}C)$ with 0.1 M phosphate buffer and inoculated cells in beef. The maximum populations were observed at 12 hr when E. coli O157:H7 was incubated in the tryptic soy broth at $37^{\circ}C$. In the case of the frozen cells at logarithmic phase, the $D_{10}$ and $12D_{10}$ values of four kinds of E. coli O157:H7 were $0.09{\sim}0.15\;kGy$ and $1.08{\sim}1.80\;kGy$, and inactivation factors were $13.33{\sim}22.22$ and $20.00{\sim}33.33$ at radiation doses of 2 and 3 kGy, respectively. The radiosensitivity of inoculated E. coli O157:H7 in beef showed the $D_{10}$ value of $0.30{\sim}0.47\;kGy$, the $12D_{10}$ value of $3.60{\sim}5.64\;kGy$, and inactivation factor of $4.26{\sim}10.00$. The radiosensitivity of the frozen cells was higher than that of the inoculated E. coli O157:H7 in beef. Gamma irradiation at doses within the range of 1.5 to 3 kGy is considered to be an effective method to control E. coli O157:H7 in beef.

• Bulletin of the Korean Chemical Society
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• v.16 no.7
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• pp.625-630
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• 1995

α-Linked D-altropyranosidic derivatives were obtained by configurational change at C-3 of α-D-mannopyranosides as the key step in preparation of allyl and methyl α-D-glycopyranosides of 6-deoxy-D-altro-heptose. The manno-altro conversion was effected by sequential reactions of Swern oxidation and stereoselective borohydride reduction. Allyl 4,6-O-benzylidene-2-O-p-methoxybenzyl-α-D-mannopyranoside was transformed to the corresponding altropyranoside via 3-oxo-arabino-hexopyranoside. Allyl 7-O-benzyl-6-deoxy-3,4-O-isopropylidene-α-D-altro-heptopyranoside has been prepared as a glycosyl acceptor to be coupled with β-D-GlcpNAc-(1→3)-α-D-Galp glycosyl donor for the synthesis of an O-antigen repeating unit of Campylobacter jejuni serotypes O:23 and O:36. Stereoselective borohydride reduction also succeeded in yielding methyl 2,4,7-tri-O-benzyl-6-deoxy-α-D-altro-heptopyranoside from the corresponding 3-oxo-α-D-arabino-heptopyranoside. C-6 Homologation was achieved by sequential reactions of cyanide displacement of 6-sulphonates, reduction of the resulting heptopyranosidurononitrile with diisobutylaluminum hydride, hydrolysis of the imine, and further reduction with sodium borohydride.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.15 no.2
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• pp.190-197
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• 2002

In this thesis, ZnO varistors with various formulation, such as A∼E, were fabricated according to ceramic fabrication method. The microstructure, electrical properties, and surge characteristics of ZnO varistors were investigated according to ZnO varistors with various formulation. In the microstructure, A∼E\`s ZnO varistor ceramics sintered at 1130$\^{C}$ was consisted of ZnO grain(ZnO), spinel phase (Zn$\_$2.33/Sb$\_$0.67/O$\_$4/), Bi-rich phase(Bi$_2$O$_3$) and intergranuler phase, wholly. Lightning impulse residual voltage of A, B, C and E\`s ZnO varistors suited standard characteristics, below 12kV at current of 5kA. On the contrary, D\`s ZnO varistor exhibited high residual voltage as high reference voltage. In the accelerated aging test, leakage current and watt loss of B, C and D\`s ZnO varistors increases abruptly with stress time under the first a.c. stress(115$\^{C}$/3.213kV/300h). Consequently, C varistor exhibited a thermal run away. On the contrary, leakage current and watt loss of A and C\`s ZnO varistors which show low initial leakage current exhibited constant characteristics. After high current impulse test, A\`s ZnO varistor has broken the side of varistor but impulse current flowed. On the contrary, E\`s ZnO Varistor exhibited good discharge characteristics which the appearance of varistor was not wrong such as puncture, flashover, creaking and other significant damage. After long duration impulse current test, E\`s ZnO varistor exhibited good discharge characteristics which the appearance of varistor was not wrong such as puncture, flashover, creaking and other significant damage. After high current impulse test and long duration impulse current test, E\`s ZnO varistor exhibited very good characteristics which variation rate of residual voltage is 1.4% before and after test.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2013.05a
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• pp.1391-1392
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• 2013

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.489-494
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• 2001

In this thesis, the microstructure and electrical properties of ZnO varistors were investigated according to ZnO varistors with various formulation. A∼E's ZnO varistor ceramics were exhibited good density, 95% of theory density and low porosity, 5%, wholly. The average grain size of A-E's ZnO varistor ceramics exhibited 11.89$\mu\textrm{m}$, 13.57$\mu\textrm{m}$, 15.44$\mu\textrm{m}$, 11.92$\mu\textrm{m}$, 12.47$\mu\textrm{m}$, respectively. Grain size of C's ZnO varistor is larger and grain size of A and D's are smaller than other varistors. In the microstructure, A∼E's ZnO varistor ceramics sintered at l130$^{\circ}C$ was consisted of ZnO grain(ZnO), spinel phase(Zn$\sub$2.33/Sb$\sub$0.67/O$_4$), Bi-rich Phase(Bi$_2$O$_3$) and inergranular phase, wholly. Reference voltage of A∼E's ZnO varistor sintered at 1130$^{\circ}C$ decreased in order D, E > A > B > C's ZnO varistors. Nonlinear exponent of varistors exhibited high characteristics, above 30, wholly. Consequently, C's ZnO varistor exhibited good nonlinear exponent, 68. Lightning impulse residual voltage of A, B, C and E's ZnO varistors suited standard characteristics, below 12kV at current of 5kA.