• 대한수의학회지
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• 제44권4호
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• pp.607-613
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• 2004

Helicobacter pylori (H. pylori)-infection is an important pathogen of stomach cancer after chronic gastritis and ulceration in the stomach and duodenum. However, the virulences of H. pylori strains have not been well-defined between clinical isolates. This study was designed to establish water-immersion-restraint stress (WIRS) model in mongolian gerbil for comparison of pathogenicity of H. pylori strains. To determine an optimal duration time for WIRS model in gerbil, 5-week-old Mongolian gerbils were divided into different groups by WIRS duration time. After graded duration of WIRS, the macroscopic ulcer index (UI) was measured with the stomach and duodenum of sacrificed animal. There were no significant differences between male and female in same duration group. However, the UI increased significantly in a time-dependent fashion. The group of 6 hours-WIRS animals showed severe hemorrhage and ulceration in their stomach and duodenum. On the other hand, the very mild lesions induced in 2 hours-treated animals. Therefore, we determined an optimal duration time for WIRS model in gerbil as 4 hours. Thereafter, we evaluated whether this WIRS model in gerbil could be used as an useful tool for in vivo comparison of pathogenicity of H. pylori strains by enhancement of pathological severity in H. pylori-infected gerbils. Mongolian gerbils were divided into H. pyloriinfected and PBS-inoculated groups. Thereafter, they were divided again into 4 hours-WIRS and no WIRS subgroups. After treatment, the severity of pathological changes was evaluated in a same manner with previous duration-determining experiment. When the animals were exposed to WIRS, the UI was significantly higher in the infected group than in the uninfected group. These results suggested that the established gerbil-WIRS model in this study enhanced effectively the severity of pathogenic changes in the H. pylori-infected Mongolian gerbils and could be used as an useful tool for in vivo comparison of pathogenicity of H. pylori strains.

• 한국어병학회지
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• 제22권2호
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• pp.115-124
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• 2009

넙치 병어에서 Photobacterium damselae subsp. damselae와 Vibrio spp.(V. anguillarum, V. splendidus, V. harveyi and V. ordalii)를 분리한 후 in vivo에서 병원성을 비교하였다. 분리균을 인위감염 한 결과, 폐사율, 혈청의 ALT, AST, cortisol 농도가 vibrio 감염구에 비하여 P. damselae 감염구에서 높게 나타났다. 또한, P. damselae 감염구에서 비특이적 면역반응인 식세포의 nitroblue tetrazolium(NBT) 반응과 혈청의 라이소자임 활성이 유의적으로 낮게 나타났다. 따라서, P. damselae는 특이적 효소인 damselysin의 분비로 높은 용혈능과 phospholipase 활성, 감염 시 내부 장기의 손상에 의한 ALT와 AST 상승, cortisol 농도의 증가로 인한 면역기능 저하가 높은 병원성을 나타낸 것으로 사료된다.

• 수산해양교육연구
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• 제24권4호
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• pp.591-601
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• 2012

양식 넙치에 Edwardsiella tarda 또는 Streptococcus iniae를 단독 또는 혼합감염하여 넙치에서 병원성을 비교하였다. 넙치에 단독 또는 혼합감염 후 혈액생화학적 성상으로 alanine aminotransferase (ALT), aspatate aminotransferase (AST), glucose 농도, total protein 농도를 조사하였으며, 라이소자임 활성, 신장과 비장 조직 중의 세균수, 조직병리학적 변화와 누적폐사율을 조사하였다. 혼합감염구는 다른 시험구에 비하여 누적폐사율, 신장과 비장 조직 중의 세균수, AST활성과 병리조직학적 변화가 크게 나타났으나, 라이소자임 활성에서는 유의적인 차이가 보이지 않았다. 따라서 E. tarda와 S. iniae의 혼합감염은 신장과 비장 조직 중의 세균수 증가와 내부 장기의 손상으로 숙주에 높은 병원성을 나타낸 것으로 판단된다.

• The Plant Pathology Journal
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• 제37권4호
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• pp.365-374
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• 2021

White rot or stem rot caused by Sclerotinia sclerotiorum is one of the most destructive fungal diseases that have become a serious threat to the successful cultivation of oilseed Brassicas. The study was designed with an aim to investigate the association between the pathogenic aggressiveness and pathogenicity determinants of this pathogen specifically in Brassica for the first time. For this, a total of 58 isolates of S. sclerotiorum from different geographical regions were collected and purified. These isolates were inoculated on a Brassica juncea cv. RL-1359 and they exhibited high level of variation in their disease progression. The isolates were grouped and then 24 isolates were selected for the biochemical analysis of pathogenicity determinants. The isolates varied significantly with respect to their total organic acids, oxalic acid production and pectin methyl esterase and polygalacturonase activity. The oxalic acid production corresponded to the disease progression of the isolates; the isolates with higher oxalic acid production were the more aggressive ones and vice-versa. This is, in our knowledge, the first study to establish a correlation between oxalic acid production and pathogenic aggressiveness of S. sclerotiorum on B. juncea. However, the pectinases' enzyme activity did not follow the trend as of disease progression. These suggest an indispensable role of oxalic acid in pathogenicity of the fungus and the potential to be used as biochemical marker for preliminary assessment of pathogenic aggressiveness of various isolates before incorporating them in a breeding program.

• The Plant Pathology Journal
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• 제38권2호
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• pp.90-101
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• 2022

Pathogenicity of eight Bacillus strains to seedlings of four cotton cultivars was evaluated under greenhouse conditions. Each of the tested cultivars was individually treated with powdered inoculum of each bacterial strain. Untreated seeds were planted as control treatments in autoclaved soil. Effects of the tested strains on levels and activities of some biochemical components of the infected seedlings were also assayed. The biochemical components included total soluble sugars, total soluble proteins, total free amino acids, peroxidase, polyphenol oxidase, phenols, and lipid peroxidation. ANOVA showed that Bacillus strain (B) was a very highly significant source of variation in damping-off and dry weight. Cotton cultivar (V) was a nonsignificant source of variation in damping-off while it was a significant source of variation in dry weight. B × V interaction was a significant source of variation in damping-off and a nonsignificant source of variation in dry weight. Bacillus strain was the most important source of variation as it accounted for 59.36 and 64.99% of the explained (model) variation in damping-off and dry weight, respectively. The lack of significant correlation between levels and activities of the assayed biochemical components and incidence of damping-off clearly demonstrated that these biochemical components were not involved in the pathogenicity of the tested strains. Therefore, it was hypothesized that the pathogenicity of the tested strains could be due to the effect of cell wall degrading enzymes of pathogenic toxins. Based on the results of the present study, Bacillus strains should be considered in studying the etiology of cotton seedling damping-off.

• Mycobiology
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• 제31권2호
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• pp.113-118
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• 2003

Solanaceous crops grown in greenhouses and fields in Korea were surveyed from 1994 to 2000. Sclerotinia rot most severely occurred up to 60% in potato. Incidence of the disease was as high as 20% at its maximum in tomato and 5% in eggplant, but as low as less than 1% in red pepper. Symptoms of Sclerotinia rot commonly developed on stems of the solanaceous crops but rarely on fruits of eggplant and tomato. A total of 169 isolates of Sclerotinia species was obtained from the diseased solanaceous crops. Out of the isolates, 165 isolates were identified as S. sclerotiorum, and the others as S. minor based on their morphological and cultural characteristics. S. sclerotiorum was isolated from all the solanaceous crops, while S. minor was only isolated from tomato. Eight isolates of S. sclerotiorum and two isolates of S. minor were tested for their pathogenicity to the solanaceous crops by artificial inoculation. All the isolates of the two Sclerotinia spp. induced rot symptoms on stems of the solanaceous crops tested, which were similar to those observed in the fields. The pathogenicity tests revealed that there was no significant difference in the susceptibility of the solanaceous crops to the isolates of S. sclerotiorum. However, in case of S. minor, the potato cultivar Sumi was relatively less susceptible to the pathogen.

• Mycobiology
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• 제42권1호
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• pp.66-72
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• 2014

Roselle (Hibiscus sabdariffa L.) family Malvaceae is an important crop used in food, cosmetics and pharmaceutics industries. Roselle is cultivated mainly in Upper Egypt (Qena and Aswan governorates) producing 94% of total production. Root rot disease of roselle is one of the most important diseases that attack both seedlings and adult plants causing serious losses in crop productivity and quality. The main objective of the present study is to identify and characterize pathogens associated with root rot and wilt symptoms of roselle in Qena, Upper Egypt and evaluate their pathogenicity under greenhouse and field condition. Fusarium oxysporum, Macrophomina phaseolina, Fusarium solani, Fusarium equiseti and Fusarium semitectum were isolated from the natural root rot diseases in roselle. All isolated fungi were morphologically characterized and varied in their pathogenic potentialities. They could attack roselle plants causing damping-off and root rot/wilt diseases in different pathogenicity tests. The highest pathogenicity was caused by F. oxysporum and M. phaseolina followed by F. solani. The least pathogenic fungi were F. equiseti followed by F. semitectum. It obviously noted that Baladi roselle cultivar was more susceptible to infection with all tested fungi than Sobhia 17 under greenhouse and field conditions. This is the first report of fungal pathogens causing root rot and vascular wilt in roselle in Upper Egypt.

• 한국식물병리학회:학술대회논문집
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• 한국식물병리학회 2003년도 정기총회 및 추계학술발표회
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• pp.112.3-113
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• 2003

More than 30 isolates of Alternaria were obtained from various solanaceous crops in Korea. For all isolates, morphological characteristics of the conidia were determined and compared with those of representative isolates of A. solani and A. tomatophila. Pathogenicity test was performed to Potato, tomato, egg plant and red Pepper and molecular characteristics of them including the representative isolates were determined using sequence analyses of ITS rDNA and histone H3 gene, and URP-PCR analysis. Based on morphological characteristics, the isolates from the solanaceous crops were grouped as identical or very similar to either A. tomatophila(ATO), A. solani(ASO), and unidentified Altemaria sp.(ASP). Among the molecular markers used in this study, the URP-PCR analysis was found to be appropriate for taxonomic resolution of these species. Based on the conidial morphology, pathogenicity test and molecular characteristics, A. tomatophila(early blight of tomato) could be distinguished from A. solani(early blight of potato), and the Alternaria sp.(ASP) from potato, which was closely related to A. solani in conidial morphology, was considered as a new species.

• 한국식물병리학회:학술대회논문집
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• 한국식물병리학회 2003년도 정기총회 및 추계학술발표회
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• pp.84.1-84
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• 2003

Magnaporthe grisea, the casual agent of rice blast, forms an appressorium to penetrate its host. Much has been learned about environmental cues and signal transduction pathways, especially those involving CAMP and MAP kinases, on appressorium formation during the last decade. More recently, pharmacological data suggest that calcium/calmodulin-dependent signaling system is involved in its appressorium formation. To determine the role of phosphoinositide-specific phospholipase C (PI-PLC) on appressorium formation, a gene (WPLCl) encoding PI-PLC was cloned and characterized from M. grisea strain 70-15. Sequence analysis showed that MPLCl has alt five conserved domains present in other phospholipase C genes from several filamentous fungi and mammals. Null mutants (mplcl) generated by targeted gene disruption exhibited pleiotropic effects on conidial morphology, appressorium formation, fertility and pathogenicity. mplcl mutants developed nonfunctional appressoria and are also defective in infectious growth in host tissues. Defects in appressorium formation and pathogenicity in mplcl mutants were complemented by a mouse PLCdelta-1 cDNA under the control of the MPLCl promoter. These results suggest that cellular signaling mediated by MPLCl plays crucial and diverse roles in development and pathogenicity of M. grisea, and functional conservation between fungal and mammalian Pl-PLCs.

• 대한미생물학회지
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• 제34권5호
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• pp.471-478
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• 1999

Spirochetes were isolated from the midgut of Ixodes persulcatus ticks captured at Chungju, Korea and identified as Borrelia afzelii strains by polymerase chain reaction. To determine the pathogenicity of the B. afzelii strains isolated in Korea, the microbiological and pathological features of Lyme disease were observed in C3H/He mice after intraperitoneal inoculation of the fresh isolate of B. afzelii strain. The results are summarized as follows 1) The Borrelia were detected in the tissues of heart, spleen, kidney, urinary bladder and knee joint within 7 days after inoculation of infection by dark field microscopic examination. The isolation rate from heart, urinary bladder and joint was significantly higher than the rate from spleen, kidney, and blood samples. 2) The Borrelia was detected in heart muscle by indirect immunofluorescent antibody test. 3) Antibody to the Borrelia was detected as early as one week after inoculation. 4) The marked tropism of the Borrelia was observed in myocardial, urinary tract and joint tissue. The main pathological features are inflammation in tissues of heart, kidney, joint and urinary bladder. From these results, the Borrelia afzelii strain isolated in Korea were determined as pathogenic strain.