• Journal of Life Science
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• v.9 no.2
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• pp.169-175
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• 1999

Salmonella typhimurium can encounter a wide variety of environments during its life cycle. In nature, S. typhimurium can experience and survive dramatic acid stresses that occur in diverse ecological niches ranging from pond water to phagolysosomes. These survival mechanism is aquired by the Acid Tolerance Response(ATR) in Salmonella. The ATR of S. typhimurium is a complex inducible phenomenon in which exposures to slight or moderate low pH will produce a stress response capable of protecting the organism against more severe acid challenges. ATR in Salmonella has two different systems that are called RpoS dependent and independent. We found that ATR in anaerobic was showed RpoS independent because rpoS$\Omega$AP had ATR as S. typhimurium UK1. Using the P22 MudJ(Km, lacZ) operon fusion technique and a lethal selection procedure combining low pH(pH4.5) and sodium acetate(10mM, pH4.5), we isolated LF487 aatA::MudJ which showed acid sensitive in anaerobic condition. aatA locus was determined at 12 min on Salmonella Genetic Map. The survival rate of aatA mutant was showed significantly diminished at pH4.3 than virulent wild type Salmonella in anaerobic condition(5% $CO_2$, 5% H$_2$, 90% $N_2$). Therefore isolated gene was confirmed important gene for anaerobic ATR system.

• Korean Journal of Food Science and Technology
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• v.29 no.1
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• pp.32-37
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• 1997

The rate constants and activation energies for formation of two chemical markers, M-1 and M-2 at sterilization temperatures were determined in a meatball system. Destruction rates for bacterial spores were also determined. The rate constants for M-1 and M-2 formation at $121^{\circ}C$ were 0.03 and 0.28 Abs/min, respectively. The activation energies for M-1 and M-2 were 27.9 and 24.6 Cal/mol. M-2 was formed faster than M-1 and reached a maximum and decreased. M-1 formation continued up to 30 min at $121^{\circ}C$ and 10 min at $131^{\circ}C$, which makes M-1 a more useful chemical marker for high $F_0$ values. The D-values for spores (B. stearothermophilus ATCC 12980) at 111, 114.4, 117.7 and $121^{\circ}C$ were 7.5, 4.5, 1.9 and 0.58 respectively. At temperatures between 111 and $121^{\circ}C$, there was a liner correlation between destruction of the spores and the M-1 formation. It was difficult to get accurate D-value at $126^{\circ}C\;and\;131^{\circ}C$, because almost all spores were dead before temperature at the center of the meatball reached $126^{\circ}C$. These data suggest that the chemical marker should be used to evaluate overprocessing as well as microbial lethality in aseptic processing.

• Parasites, Hosts and Diseases
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• v.58 no.3
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• pp.301-308
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• 2020

Owing to global climate change, the global resurgence of vector-borne infectious diseases and their potential to inflict widespread casualties among human populations has emerged as a pivotal burden on public health systems. Tsutsugamushi disease (scrub typhus) in the Republic of Korea is steadily increasing and was designated as a legal communicable disease in 1994. The disease is a mite-borne acute febrile disease most commonly contracted from October to December. In this study, we tried to determine the prevalence of tsutsugamushi disease transmitted by chigger mites living on rodents and investigated their target vector diversity, abundance, and distribution to enable the mapping of hotspots for this disease in 2015. A total of 5 species belonging to 4 genera (109 mites): Leptotrombidium scutellare 60.6%, L. pallidum 28.4% Neotrombicula tamiyai 9.2%, Euschoengastia koreaensis/0.9%), and Neoschoengastia asakawa 0.9% were collected using chigger mite collecting traps mimicking human skin odor and sticky chigger traps from April to November 2015. Chigger mites causing tsutsugamushi disease in wild rodents were also collected in Hwaseong for the zoonotic surveillance of the vector. A total of 77 rodents belonging to 3 genera: Apodemus agrarius (93.5%), Crocidura lasiura (5.2%), and Micromys minutus (1.3%) were collected in April, October, and November 2015. The most common mite was L. pallidum (46.9%), followed by L. scutellare (18.6%), and L. orientale (18.0%). However, any of the chigger mite pools collected from rodent hosts was tested positive for Orientia tsutsugamushi, the pathogen of tsutsugamushi disease, in this survey.

• Korean Journal of Plant Tissue Culture
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• v.24 no.1
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• pp.37-41
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• 1997

The in vitro regeneration and genetic transformation systems in hot pepper(Capsicum annuum L.) have not been routinely available, which has been a major limiting factor in the application of new genetic manipulations. An efficient procedure to regenerate whole pepper plants and to generate transgenic plants expressing a foreign gene was established. A relatively high frequency of plant regeneration was observed when hypocotyl and cotyledon explants were cultured on MS medium supplemented with NAA 0.1 mg/L plus zeatin 2.0 mg/L or IBA 10.0 mg/L plus BAP 1.0 mg/L. Addition of AgNO$_3$5 $\mu$M to these media improved the regeneration frequency up to 8%. For plant transformation, hypocotyl and cotyledon explants of hot pepper were precultured on shoot induction media without kanamycin added for 2 days, and then cocultured with Agrobacterium tumefaciens pDY183 for 2 days. Putative transformants were obtained from selection media containing 100 mg/L kanamycin sulfate and 500 mg/L carbenicillin. Putatively selected transformants were confirmed by amplification of selectable marker genes (ADA and NPT II) by polymerase chain reacion. Successful transcripts of ADA gene were detected by Northern blot analysis. Enzyme activity of ADA was also examined by spectrophotometric analysis, and expression of ADA gene in hot pepper suggests the potential application of ADA gene as a selectable marker in plants.

• Korean Journal of Plant Tissue Culture
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• v.24 no.2
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• pp.71-75
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• 1997

For the establishment of early selection of heat-tolerant clones through in vitro tuberization of true potato seeds, different temperature treatments for in vitro tuberization were investigated. The ratios of tuberization at 2$0^{\circ}C$ on var. Superior and DTO-33 treated with 5 mg/L of BAP and 500 mg/L of CCC, were 85% and 92%, respectively. At 3$0^{\circ}C$, the ratio of tuberization on DTO-33 was 37%, which revealed strongly heat-tolerant clone. In culture system of in vitro tuberization, the number of tubers per flask at 2$0^{\circ}C$ on non-subculture incubation was more than that on subculture incubation. The condition of non-subculture and short-day treatment for 4 weeks was good for production as 10.6 tubers per flask, which was very similar to that of long-day treatment. On the other hand, tuber diameter on long-day treatment was greater as 11.2 mm than on short-day treatment. Therefore, in vitro tuberization from true potato seeds could be induced under the condition of long-day treatment at darkness.

• Korean Journal of Microbiology
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• v.34 no.3
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• pp.108-114
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• 1998

Salmonella Pathgenicity Island 2 plays an important role in Salmonella pathogenicity, especially invasion into host cell. We have investigated the effect of various environmental factors, such as oxygen level, osmolarity, pH, carbon starvation and glycerol addition on the expression of SPI2. For this research, we constructed the reporter plasmids, in which the promoter-less lac operons are fused with the regulatory regions (including promoter) of ssaJ and ssaK, major genes in SPI2. The study using the reporters showed that low oxygen, low osmolarity, or weak alkali conditions increased the expression levels of ssaJ and ssaK and when these three conditions exist simultaneously, the expression levels of ssaJ and ssaK are the highest. However carbon starvation and glycerol addition did not affect the expression of ssaJ and ssaK. These environmental effects on the expression levels of ssaJ and ssaK are the same in three Salmonella typhimurium wild types, LT2, UK1, and SL1344. In addition, we confirmed that the mutation in hilA, a regulatory gene encoding a transcriptional activator of SPI1, had no effect on the expression of ssaJ and ssaK. Thus, these results strongly suggest that the expressions of SPI2 and SPI1 are regulated by different control systems.

• Journal of Korean Society of Rural Planning
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• v.13 no.3
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• pp.123-133
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• 2007

The purpose of this study is to develop the landscape resource assessment system(LRAS) to help evaluate the value of landscape resources(Jeju Island's Stonewall fencing farming land) for the introduction of direct payment system of the landscape preservation objectively and to applicate the model in the fields. Delphi survey on Jeju's stonewall experts shows that the order of priority among value evaluation elements on Jeju's stonewall is its harmony with surroundings(34%), the preservation of its original state(34%) and its density and scale(32%). Evaluation system development of landscape resources(Jeju's stonewall fencing filming land) and field observation survey utilizing it consists of the following five steps. Step 1 includes the first Delphi survey on Jeju's stonewall experts to decide its value evaluation elements and their priority. Step 2 is the second Delphi survey on Jeju's stonewall experts to grade pictures of landscape resources(Jeju's stonewall fencing farming land) on the basis of expert-proposed value evaluation standards. Step 3 consists of analysis work using the result of Delphi survey on experts. Step 4 is to select five grade standard pictures according to each of three grading elements of A, B, C belonging to each of the three standards. Then, it is necessary to make panels including five A-grade pictures, five B-grade pictures and five C-grade pictures according to each of the three elements of density, harmony, and original state preservation. Step 5 consists of field observation survey. According to the result of few experts' value evaluation of stonewall fencing farming land with the aid of NRAS developed in this research, the area of Pyeongdae-ri is ranked first, and then the area of Bukcheon-ri, Chocheon-up, the area of Gwakgi-ri, Ewol-up, the area of Shinum-ri, Ewol-up and the area of Yongsu-ri, hankyung-Myun are ranked in the order named. When those areas are graded, A Grade Areas includes the areas of Pyeongdae-ri, the area of Bukcheon-ri, the area of Gwakgi-ri, B Grade Areas consist of the area of Shinum-ri and the area of Yongsu-ri, and the areas of Onpyeong, wimi and youngrak belong to C Grade Area.

• Applied Biological Chemistry
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• v.36 no.6
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• pp.488-494
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• 1993

A photosynthetic bacterium strain P17 having high growth rate and assimilating ability of organic acids was isolated from several soil samples, which was identified as Rhodospirillum rubrum. Cultural conditions of the strain P17 were examined for the production of starter culture used in the treatment of organic waste water. The addition of organic acids mixture as carbon source containing 0.2% Na-acetate, 0.1% Na-propionate and 0.2% Na-lactate and 0.1% of yeast extract as growth factor stimulated the cell growth. The maximal cell production was obtained at $30^{\circ}C$, pH 7.0, 2,500 lux of illumination and $50{\sim}100\;rpm$ of agitation. Under the optimal conditions of batch and fed-batch culture systems in a Jar fermentor, 5.17 g/l and 7.93 g/l of cells were obtained after S days of cultivation, respectively. In continuous culture system, the cell productivity was 0.206 g/l/h at a dilution rate of 0.21 $h^{-1}$. When R. rubrum P17 was cultivated in a soybean curd waste water, initial COD level(3,240 mg/l) of the waste water was reduced to 250 mg/l after 4 days of cultivation.

• Reproductive and Developmental Biology
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• v.38 no.3
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• pp.129-136
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• 2014

This study was carried out to elucidate the effect of antibiotic-free rearing system(ARS) on cortisol level, stress hormone, and fatty acid content in the edible muscle tissues, that were of M. longissimus in Hanwoo. These cattle were reared in two different systems including antibiotic-free (ARS) and conservative system (CRS). To increase the experimental reliability, the muscle samples were purchased 3 times from 3 Korean brands of beef produced with ARS or CRS. In the muscle tissue, cortisol level was significantly lower in ARS than CRS, (p=0.0176). But the levels of total saturated- and unsaturated-fatty acids were not significantly different between ARS and CRS (p>0.05). Of total fatty acids, the total saturated fatty acid tended to be greater in CRS and the total unsaturated fatty acid tended to be greater in ARS. However, of the total unsaturated fatty acids, the level of n-6 unsaturated fatty acids was significantly higher in ARS than CRS (p=0.0040). Especially, ${\alpha}$-linolenic acid (ALA) and ${\gamma}$-linolenic acid (GLA) levels were significantly higher in ARS (p<0.01). The n-6 fatty acid content and cortisol level in muscle tissue were negatively correlated at p=0.0140. In conclusion, ARS may produce beef with higher quality which contains lower cortisol and greater n-6 fatty acids, such as ALA and GLA.

• Journal of Animal Science and Technology
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• v.55 no.5
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• pp.417-425
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• 2013

We sought to provide a method for freezing and preserving primordial germ cells, or an avian germ cell of a bird, as a material for developmental engineering or species preservation. The aim of this study was to compare the efficacy of slow freezing with a vitrification method for the cryopreservation of chicken primordial germ cells (PGCs). PGCs obtained from the germinal gonad of day 5.5-6 day (stage 28) cultured chick embryos, using the MACS method, were classified into two groups: slow freezing and vitrification. We examined the viability of PGCs after Cryopreservation. Four freezing methods were compared with each other, including the following: Method 1: The PGCs were frozen by a programmed freezer in a plastic straw, including 2.0 M ethylene glycol (EG) as cryoprotective additive (slow freezing) Method 2: The PGCs were vitrified in a plastic straw, including 8.0 M EG, plus 7% polyvinylpyrrolidone (PVP) (rapid freezing). Method 3: The slow freezing was induced with a cryotube including 2.0 M EG Method 4: The PGCs were frozen in a cryotube including 10% dimethyl suloxide (DMSO) (rapid freezing). After freezing and thawing, survival rates of the frozen-thawed PGCs from Method 1 to 4were 76.4%, 70.6%, 80.5% and 78.1% (p<0.05), respectively. The slow freezing ($-80^{\circ}C$ programmed freezer) method may provide better survival rates of frozen-thawed PGCs than the vitrification method for the cryopreservation of PGCs. Therefore, these systems may contribute to the cryopreservation of a rare avian species.