• BMB Reports
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• v.39 no.1
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• pp.9-15
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• 2006

To prove whether error catastrophe /lethal mutagenesis is the primary antiviral mechanism of action of ribavirin against foot-and-mouth disease virus (FMDV). Ribavirin passage experiments were performed and supernatants of $Rp_1$ to $Rp_5$ were harvested. Morphological alterations as well as the levels of viral RNAs, proteins, and infectious particles in the BHK-21 cells infected using the supernatants of $Rp_1$ to $Rp_5$ and control were measured by microscope, real-time RT-PCR, western-blotting and plaque assays, respectively. The mutation frequency was measured by sequencing the complete P1- and 3D-encoding region of FMDV after a single round of virus infection from ribavirin-treated or untreated FMDV-infected cells. Ribavirin treatment for FMDV caused dramatically inhibition of multiplication in cell cultures. The levels of viral RNAs, proteins, and infectious particles in the BHK-21 cells infected were more greatly reduced along with the passage from $Rp_1$ to $Rp_5$, moreover, nucleocapsid protein could not be detected and no recovery of infectious virus in the supernatant or detection of intracellular viral RNA was observed at the $Rp_5$-infected cells. A high mutation rate, giving rise to an 8-and 11-fold increase in mutagenesis and resulting in some amino acid substitutions, was found in viral RNA synthesized at a single round of virus infection in the presence of ribavirin of $1000\;{\mu}M$ and caused a 99.7% loss in viral infectivity in contrast with parallel untreated control virus. These results suggest that the antiviral molecular mechanism of ribavirin is based on the lethal mutagenesis/error catastrophe, that is, the ribavirin is not merely an antiviral reagent but also an effective mutagen.

• Parasites, Hosts and Diseases
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• v.23 no.1
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• pp.79-86
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• 1985

In order to judge appropriately the suitability as the second intermediate host of Clonorchis sinensis, the present experiments were proposed to survey the metacercaria of C. sinensis in the fish host, Cuztriculus eigenmanni, in the 6eld, and to observe, by experimental infection of the fish with Clonorchis cercaria, the penetrating ability of the cercaria, maturity, the process of degeneration and extinction, and infectivity of the metacercaria. The following is a brie summary of the leading facts gained through the experiments. 1. All the ten fish (mean body weight $13.4{\pm}3.439$) which were caught in Ok-ku irrigation reservoir were in acted with the metacercariae and the average number of the metacercariae found in the fish body/gram was 4.55. 2. The Bish was easily subject to invasion of the cercaria, and the examination of the cercariae after having the fish infected disclosed that 5:l hours after the infection, all of the cercariae formed their cysts in muscle and the metacercariae kept growing, that 7 days later the metacercariae were found folding their bodies twice, and that in 15 days the characteristic structure of the metacercariae was complete and made a vigorous rotary movement intermittently. 3. In the case of control fish, Pseudorasbora parka, both penetrating ability of the cercariae and the infective degree of the metacercariae to control host were stronger as compared with the 5sh host because that the control fish had higher suceptibility to C. sinensis. 4. Afterwards, the metacercariae in the fish host came to a state of maturity and beyond this stage some metacercariae started the Process of degeneration and extinction in as early as 30 days, and as more days elapsed, mortality of the metacercariae was not uniformly increased but difference of mortality appeared to be according to the individual of Ssh host. That is, in 390, 540 and 586 days, all of the metacercariae in the fish hosts became dead, meanwhile almost all of those found in the fish host of 596 days after the infection survived (mortality; 8, 51%) , Percentage of orally administered metacercariae developing to maturity in rabbit is 10.465 in the last case. 5. As the days were progressed the shapes of the metacercariae in the fish host tended to change from ellipsoid to almost round shapes, the length became shorter while the width was wider. The results shown above revealed that C. eigenmanni was, though it could not be proper host than p. larva. suitable as the second intermediate host in addition to our previous observation results.

• Journal of Microbiology and Biotechnology
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• v.23 no.8
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• pp.1159-1166
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• 2013

Orientia tsutsugamushi, a gram-negative bacterium, causes severe acute febrile illness in humans. Despite this danger, the route of infection, infectivity, and protective mechanisms of the host's immune response to O. tsutsugamushi are unclear. Dendritic cells (DCs) are one of the most important cell types in bridging the innate and adaptive immune responses. In this study, we observed that O. tsutsugamushi infects and replicates in monocyte-derived DCs (MODCs). During infection and replication, the expressions of the cytokines IL-12 and TNF-${\alpha}$, as well as the co-stimulatory molecules CD80, CD83, CD86, and CD40, were increased in MODCs. When O. tsutsugamushi-treated MODCs were co-cultured with autologous $CD4^+$ T cells, they enhanced production of IFN-${\gamma}$, a major Th1 cytokine. Collectively, our results show that O. tsutsugamushi can replicate in MODCs and can simultaneously induce MODC maturation and increase proinflammatory cytokine levels in MODCs that subsequently activate $CD4^+$ T cells.

• Research in Plant Disease
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• v.17 no.2
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• pp.211-215
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• 2011

Cucumber mosaic virus (CMV)-like isolate was collected from Raphanus sativus (cv. Choon-hyang), which showed mosaic symptoms. The isolate was confirmed to a strain of CMV by host responses in Vigna unguiculata, Chenopodium amaranticolor and Gomphrena globosa, by viral genome composition with RT-PCR and PCR-RFLP, and by serological analysis. Symptom developed by the strain of CMV was severe in Nicotiana benthamiana, N. glutinosa, N. tabacum (cv. Samsun, cv. Xanthi), Cucumis melo (cv. Early hanover), Cucumis sativus (cv. White wonder), Capsicum annuum (cv. Chung-yang and cv. Geum-top), but mild symptom was developed in Raphanus sativus (cv. Choon-hyang), Brassica rapa ssp. pekinensis (cv. Bul-Am No. 3), and B. juncea (cv. Daenong Jukgot). Newly isolated strain of CMV could infect diverse crops including Solanaceae, Cucurbitaceae and Brassicaceae. We designated the new strain of CMV as Gn-CMV based on the novel infectivity of Brassicaceae. In double-stranded (ds) RNA analysis, Gn-CMV consisted of 3.3, 3.0, and 2.2 kb genomes likewise other strains of CMV. SDS-polyacrylamide gel electrophoresis (SDS-PAGE) showed 28 kDa of the CMV coat protein. By restriction enzyme mapping using Cac8I, ClaI and MspI of RT-PCR products indicated that Gn-CMV belongs to CMV subgroup I.

• The Plant Pathology Journal
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• v.36 no.4
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• pp.305-313
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• 2020

Host shifting and host expansion of fungal plant pathogens increases the rate of emergence of new pathogens and the incidence of disease in various crops, which threaten global food security. Magnaporthe species cause serious disease in rice, namely rice blast disease, as well as in many alternative hosts, including wheat, barley, and millet. A severe outbreak of wheat blast due to Magnaporthe oryzae occurred recently in Bangladesh, after the fungus was introduced from South America, causing great loss of yield. This outbreak of wheat blast is of growing concern, because it might spread to adjacent wheat-producing areas. Therefore, it is important to understand the host range and population structure of M. oryzae and related species for determining the evolutionary relationships among Magnaporthe species and for managing blast disease in the field. Here, we collected isolates of M. oryzae and related species from various Poaceae species, including crops and weeds surrounding rice fields, in Korea and determined their phylogenetic relationships and host species specificity. Internal transcribed spacer-mediated phylogenetic analysis revealed that M. oryzae and related species are classified into four groups primarily including isolates from rice, crabgrass, millet and tall fescue. Based on pathogenicity assays, M. oryzae and related species can infect different Poaceae hosts and move among hosts, suggesting the potential for host shifting and host expansion in nature. These results provide important information on the diversification of M. oryzae and related species with a broad range of Poaceae as hosts in crop fields.

• The Korean Journal of Nuclear Medicine
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• v.1 no.2
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• pp.61-74
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• 1967

In order to confirm whether acquired immunity or resistance can be developed by the repeated hookworm infections, the 150 mature actively moving filariform ancylostoma duodenale larvae obtained from the severe hookworm anemia patients were orally given to 8 healthy volunteers in three divided doses, 50 in each, at 5 day interval. Also the hematological changes as well as several ferrokinetics using $^{59}Fe$ were done and were compared with 10 controls. The clinical symptoms and signs were checked every day for the first 3 weeks and then twice weekly until the end of the experiment. The appearance of the ova in the stool was examined by the formalin ether method and the ova was counted by the Stoll's method. The following laboratory tests were done: 1) Red blood cell count, venous blood hematocrit(micromethod), hemoglobin count (cyanomethemoglobin method) were checked every 5 to 7 day interval. 2) Plasma iron concentration (Barkan's modified method) was determined every 2 to 3 week interval. 3) Radioisotope studies: a) Ferrokinetics: Huff et al and Bothwell's method were applied. Erythropoietic Index (% of normal)=$\frac{Subject's\;turnover/100ml\;whole\;blood{\times}100}{Average\;normal\;turnover/100ml\;whole\;blood}$ of the gastrointestinal absorption of iron: Radioiron($^{59}Fe$) balance b) Quantitative measurement method was applied. c) Determination of the plasma erythropoietin activity: Fried's method was applied. Following were the results: 1) The serum iron level was lower. The red cell volume was decreased, but with relative increase of plasma volume. 2) The plasma iron disappearance time was accelerated and the plasma iron turnover rate was decreased. The red cell iron turnover rate was markedly increased, while all of the red cell iron concentration, circulating red cell iron. plasma iron pool were decreased. The daily iron pool turnover and red cell renewal rate were increased. 3) The erythropoietic index, erythropoietin activity and intestinal absorption of iron($^{59}Fe$) were markedly increased. 4) The infectivity was $9.8{\pm}1.31%$ which was lower than that observed in the single infection. 5) From these observations, it is concluded that the hookworm anemia is essentially iron deficieny in its origin and some immunity acquisition is possible with repeated infections.

• Korean journal of applied entomology
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• v.35 no.1
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• pp.80-84
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• 1996

Infectivity of entomopathogenic nematodes and fungus was evaluated against fly larvae in the laboratory and outhouses. Mortalities of Muscina stabulans larvae were 96.7f 2.8% in Steinernema glaseri Dongrae strain, 90.0+0.0% in S. carpocapsae All strain, 86.7f 2.7% in Heterorhabditis bacteriophora Hamyang strain, and 70.0+9.4% in S. carpocapsae Pocheon strain on the filter paper. When 260, 000 nem\ulcornertodes were sprayed into the outhouses, H. bacterwphora Hamyang strain killed 100%, S. glaseri Dongrae strain killed 76.9+3.9%, and S. carpocapsae Pocheon strain killed 58.5+6.1% of maggots. When 130, 000 nematodes and 7.0X lo9 cfu of entomopathogenic fungus, Beauveria brongniartii were sprayed alone or combined into outhouses, mortalities of maggots were 73.6+0.1% in B. brongniartii alone, 77.8+3.9% in S. carpocapsae Pocheon strain plus B. brongniartii, and 77.7f 5.1% in H. bacteriophora Hamyang strain plus B. brongniartii. Entomopathogenic nematodes and fungus were potential biological control agents in this study.

• Korean journal of applied entomology
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• v.17 no.3 s.36
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• pp.131-138
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• 1978

A virus named Cymbidium mild mosaic virus(Cy MMV), was mechanically transmitted to Chenopodium amaranticolor from the leaves of Cymbidium with mild mosaic symptoms. The virus was cultured in C. amaranticolor, in which it produced local chlorotic and ring spots, followed by systemic vein clearing with distortion. CyMMV infected 7 out of 35 species of plants. In C. amaranticolor juice infectivity was lost by heating at $90^{\circ}C$ for 10 miuntes, and by aging at$20^{\circ}C$ for 60 days, and by diluting at $10^{-6}$ when bioassayed on C. amaranticolor. CyMMV was not transmitted by Myzus persicae. The virus was purified after clarification of homogenized C. amaranticolor leaf tissues with chloroform, by differential centrifugation followed by sucrose density gradient centrifugation. Electron microscopic examination of purified preparation showed spherical particles of 28nm in diameter. The UV absorption spectrum of purified preparation was typical of u nucleoprotein (max. at 261nm. min. at 243nm), and showed 260/280=1.72 and max/min=1.26. The value of the sedimentation coefficient of the virus was S20.w=126. In gel-diffusion tests, CyMMV antiserum reacted with CarMV, but not with any of four other viruses (BBWV, CRSV, CMV, TBRV) having similar particles and properties in vitro. In ultra-thin sections of CyMMV infected tissues, a large number of virus particles were found in the cytoplasm of mesophyll cells and in xylem vessels.

• Parasites, Hosts and Diseases
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• v.48 no.4
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• pp.325-329
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• 2010

Toxoplasma gondii KI-1, a recent new isolate from Korea, shows similar pathogenicity and infectivity to mice compared to the virulent RH strain. To understand characteristics of host immunity, including immune enhancement or suppression, we investigated proliferative responses and phenotypes of spleen cells. In addition, kinetics of IFN-${\gamma}$, a Th1 cytokine, was examined in BALB/c mice up to day 6 post-infection (PI). Intraperitoneal injection of mice with $10^3$ KI-1 tachyzoites induced significant decreases (P < 0.05) in proliferative responses of spleen cells. This occurred at days 2-6 PI even when concanavalin A (con A) was added and when stimulated with KI-1 antigen, suggesting suppression of the immunity. $CD4^+$ T-cells decreased markedly at day 2 PI (P < 0.05), whereas $CD8^+$ T-cells, NK cells, and macrophages did not show significant changes, except a slight, but significant, increase of $CD8^+$ T-cells at day 6 PI. The capacity of splenocytes to produce IFN-${\gamma}$ by con A stimulation dropped significantly at days 2-6 PI. These results demonstrate that intraperitoneal injection of KI-1 tachyzoites can induce immunosuppression during the early stage of infection, as revealed by the decrease of $CD4^+$ T-cells and IFN-${\gamma}$.

• Journal of Preventive Medicine and Public Health
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• v.10 no.1
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• pp.3-15
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• 1977

In order to find out health problems among inhabitants in slum areas in Kwanak-Ku, Seoul, a series of health survey was conducted upon 510 households by interview from March to December, 1976. The results obtained were as follows: 1. Employments of householders were unstable; Out of 508 householders, 164(32.3%) were unemployed and 184 (36.2%) were daily or temporary employees. 2. Average number of households per house was 2.0 and average area of residential room per person was $4.0m^2$. 3. 476(93.3%) out of 510 households were supplied with tap water and rest of them made use of ground water as a source of drinking water. 4. Only 279(18.3%) out of 1527 live births were delivered at medical facilities, 496(32.7%) were at home attended by doctors or midwives and 358(25.1%) took prenatal care. The above findings were worse in urban slum area than in other urban area of relatively high economic level, but were better than in rural area of less medical facilities. 5. Initiation of treatment were delayed until their illnesses were advanced in most of the households, 472(92.5%) out 510. In the early stage of the illness, 131(25.6%) of the house-holds sought physicians in their clinics or general hospitals and 250 (40.9%) visited chemists, to toy drugs at first hand. Frequency of visits to physician increased to 52.8% as the disease aggravated in later stages. 6. Cost of medical expenditure per household amounted to 815 won, and was paid to, in the order of chemists, physicians, chinese herb stores, chinese herb doctors. 7. Concerning the health knowledge of the inhabitants, 273(53.9%) out of 506 respondents were aware of the infectivity of pulmonary tuberculosis, and 68(13.4%) of them checked regularly their chest findings by X-ray at least once every two years. 8. As for the family planning, although 448(87.3%) out of 510 respondents were in favor of it, 215 (41.8%) of them were actually practicing contraception. 9. About 40.6% (125 respondents) of them obtained information and knowledge concerning contraception through personal contact with family planning workers. 10. Nutritional status of housewives was generally poor: 49(38.3%) out of 128 housewives were found to be anemic and average serum protein level was $7.5{\pm}0.82g/dl$.