• Title/Summary/Keyword: Susceptibility

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Suggestions of Stone Materials for Restoration of Gwanghwamun Woldae in Seoul Based on Lithological Study (암석학적 연구를 통한 서울 광화문 월대 복원용 석재 제안)

  • Myeong Seong Lee;Yu Bin Ahn;Se Rin Park;Myoungju Choie;Jiyoung Kim
    • Economic and Environmental Geology
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    • v.56 no.6
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    • pp.647-659
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    • 2023
  • This study is to analyze the lithological similarities between railing stones of Gwanghwamun Woldae and stone blocks stored in Donggureung Royal Tombs, Guri, to interpret the provenance of the stones, and to suggest the most suitable quarry for a new stones supply among the rocks in the Seoul-Pocheon area in order to select stones for the restoration of the Gwanghwamun Woldae. The railing stones in Donggureung are medium to coarse-grained pink biotite granite, and their lithological characteristics, magnetic susceptibility(Average 5.20 ×10-3 SI unit), and gamma spectrometer data(K 5.00~6.38%, U 4.92~8.56 ppm, Th 27.60~36.44 ppm) show similarities with the remaining railing stones in Gwanghwamun Woldae(Average 5.38). Therefore, the railing stones in Donggureung can be reused for the restoration of Gwanghwamun Woldae. They have similar lithological and geochemical charateristics to the pink biotite granite found the Suraksan Mt. and Buramsan Mr. areas in Seoul, suggesting that these areas are the source of the stone. However, since the Suraksan Mt. and Buramsan Mt. areas are currently unavailable for quarrying, lithological and geochemical analyses on granite from the Yangju and Pocheon areas are conducted to determine the suitability of the new stone for restoration. As a result, a pink biotite granite similar to the Woldae stones was identified in the Pocheon area, and it is suggested that the stones similar in grain size and colour to the railing stones of Gwanghwamun Woldae should be selected and used for the restoration of Gwanghwamun Woldae.

Acute toxicity of ethyl formate to nontarget organisms and reduction effect of sodium silicate on ethyl formate-induced phytotoxicity (에틸포메이트의 비표적생물에 대한 급성독성 및 sodium silicate의 약해저감 효과)

  • Kyeongnam Kim;Yubin Lee;Yurim Kim;Donghyeon Kim;Chaeeun Kim;Yerin Cho;Junyeong Park;Yongha You;Byung-Ho Lee ;Sung-Eun Lee
    • Korean Journal of Environmental Biology
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    • v.41 no.3
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    • pp.193-203
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    • 2023
  • Ethyl formate (EF) is a naturally occurring insecticidal compound and is used to control pests introduced from abroad, in quarantine, by a fumigation method. In particular, it is mainly used as a substitute for methyl bromide and is less toxic to humans and less harmful to plants. This study aimed to investigate the possible acute toxicity of EF to useful organisms, and how to reduce phytotoxicity in watermelon, zucchini, and oriental melon. After fumigation with EF for 2 h, the LC50 values for earthworms, honey bees, and silkworms were 39.9, 7.09, and 17.9g m-3, respectively. The degree of susceptibility to EF was in the order of earthworms, silkworms, and honey bees based on the LC50 value, and EF fumigation induced stronger acute toxicity to honey bees. Phytotoxicity was observed in watermelon leaves treated with a concentration of 7.5 g m-3 EF, and when treated with a concentration of 10.0g m-3, it was confirmed that the edges of watermelon leaves were charred and seemed to be damaged by acids. Zucchini and melon, and other cucurbits, showed strong damage to the leaves when treated with a concentration of 10 g m-3, and sodium silicate, at concentrations of 10% and 20%, was used to reduce phytotoxicity. Therefore, acute toxicity towards nontarget organisms and phytotoxicity during the fumigation of EF should be reduced for efficient agricultural pest control.

Malignancy in Patients With Inborn Errors of Immunity Beyond Infectious Complication: Single Center Experience for 30 Years

  • Doo Ri Kim;Kyung-Ran Kim;Hwanhee Park;Joon-sik Choi;Yoonsun Yoon;Sohee Son;Hee Young Ju;Jihyun Kim;Keon Hee Yoo;Kangmo Ahn;Hee-Jin Kim;Eun-Suk Kang;Junhun Cho;Su Eun Park;Kihyun Kim;Yae-Jean Kim
    • Pediatric Infection and Vaccine
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    • v.30 no.3
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    • pp.129-138
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    • 2023
  • Purpose: Cancer incidence is known to be higher in patients with inborn errors of immunity (IEI) compared to the general population in addition to traditionally well-known infection susceptibility. We aimed to investigate cancer occurrence in patients with IEI in a single center. Methods: Medical records of IEI patients treated at Samsung Medical Center, Seoul, Korea were retrospectively reviewed from November 1994 to September 2023. Patients with IEI and cancer were identified. Results: Among 194 patients with IEI, seven patients (3.6%) were diagnosed with cancer. Five cases were lymphomas, 4 of which were Epstein-Barr virus (EBV)-associated lymphomas. The remaining cases included gastric cancer and multiple myeloma. The median age at cancer diagnosis was 18 years (range, 1-75 years). Among patients with cancer, underlying IEIs included X-linked lymphoproliferative disease-1 (XLP-1, n=3), activated phosphoinositide 3-kinase delta syndrome (APDS, n=2), and cytotoxic T-lymphocyte antigen 4 (CTLA-4) haploinsufficiency (n=2). Seventy-five percent (3/4) of XLP-1 patients, 40.0% (2/5) of APDS patients, and 50.0% (2/4) of CTLA-4 haplo-insufficiency patients developed cancer. Patients with XLP-1 developed cancer at earlier age (median age 5 years) compared to those with APDS and CTLA-4 (P<0.001). One patient with APDS died during hematopoietic cell transplantation. Conclusions: Cancer occurred in 3.6% of IEI patients at a single center in Korea. In addition to infectious complications and inflammation, physicians caring for IEI patients should be aware of the potential risk of cancer, especially in association with EBV infection.

Studies on the Virus in Silkworm Bombyx mori L. -Resistance to Virus Disease- (가잠 Virus에 관한 연구 -저항성에 관한 기초조사-)

  • 박광의;강석권
    • Journal of Sericultural and Entomological Science
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    • v.9
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    • pp.67-87
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    • 1969
  • 1. Objectives and Importance. Many silkworms have been damaged by nuclear polyhedrosis virus diseases thoughout the country every year causing a decease in cocoon production by approximately ten per cent per year. The damage caused by the infections virus has occured in spite of complete disinfection. In this respect, it is well known it is impossible, at the present time, to protect the silkworm from these virus infections through chemical and physical control methods. Therefore, this author has attempted to solve this urgent problem from the view point of heredity and breeding, discovering the different resistances and heritabilities among 120 stains collected from throughout the country, and selecting the ones with highest resistance for the basic materials in the silkworm breeding. 2. Results of work 1) The strains with strong resistance to the nuclear polyhedrosis virus diseases are N$_4$, N$\sub$15/, N$\sub$48/, C$\sub$55/ and Em. the log ED$\sub$50/ values of them vary between 0.799 and 1.611. The susceptible strains are N$\sub$20/, C$\sub$62/, N$\sub$76/, N$\sub$79/ and C$\sub$108/, the log ED$\sub$50/ values of them vary between 5.159 and 7.258. (Reference Table 4) The Japanese strain with a log ED$\sub$50/, value of 3.770 is the strongest, followed by the Chinese strain with a log ED$\sub$50/ value of 3.564. The weakest is the European strain with a log ED$\sub$50/ value of 3.3381. The direction coefficient of the regression equation of the susceptibility varies between 0.1 and 0.6, the uniformness of the resistance of the preserved strains of this country is comparatively low. The hereditary henomena of the resistance of each strain and the conerete method of its application for silkworm breeding main the subjects for later studies. 2) The content of water and ash in silkworm has not been correlated with the capability for resistance to the virus diseases(Reference. Table 8). but it is very significantly correlated with mortality rate (in common reaning). In the case of the silkworms which have just completed the fourth moulting the content of water and ash is not related to the mortality rate. In the case of the silkworms which have just completed the third moulting, however, the water( +0.326) and ash (+0.362) registered a high significance. The ash content in the first ($\div$0.520) and second ($\div$0.386) moults is highly significant but water content in both cases is not significant (Reference Table 7). 3) The No. 205 strain proved to be the best in character among the various F$_1$ hybrids. No. 204 was very good in strength but a little lower in cocoon character than the control. No. 212 was a little low in coccon character and mortality was average, but the cocoon harvest was the best among all the varieties offered for (Reference Table 9). 4), In short, the above mentioned strains which are known to have strong resistance to the virus disease are expected to provide basic data for breeding strong varieties. It is proposed that continued research should be conducted on the characteristics of various strains for a satisfactory preservation of various characteristics.research should be conducted on the characteristics of various strains for a satisfactory preservation of various characteristics.

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Analysis of Foodborne Pathogens in Food and Environmental Samples from Foodservice Establishments at Schools in Gyeonggi Province (경기지역 학교 단체급식소 식품 및 환경 중 식중독균 분석)

  • Oh, Tae Young;Baek, Seung-Youb;Koo, Minseon;Lee, Jong-Kyung;Kim, Seung Min;Park, Kyung-Min;Hwang, Daekeun;Kim, Hyun Jung
    • Journal of the Korean Society of Food Science and Nutrition
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    • v.44 no.12
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    • pp.1895-1904
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    • 2015
  • Foodborne illness associated with food service establishments is an important food safety issue in Korea. In this study, foodborne pathogens (Bacillus cereus, Clostridium perfringens, Escherichia coli, pathogenic Escherichia coli, Listeria monocytogenes, Salmonella spp., Staphylococcus aureus, and Vibrio parahaemolyticus) and hygiene indicator organisms [total viable cell counts (TVC), coliforms] were analyzed for food and environmental samples from foodservice establishments at schools in Gyeonggi province. Virulence factors and antimicrobial resistance of detected foodborne pathogens were also characterized. A total of 179 samples, including food (n=66), utensil (n=68), and environmental samples (n=45), were collected from eight food service establishments at schools in Gyeonggi province. Average contamination levels of TVC for foods (including raw materials) and environmental samples were 4.7 and 4.0 log CFU/g, respectively. Average contamination levels of coliforms were 2.7 and 4.0 log CFU/g for foods and environmental swab samples, respectively. B. cereus contamination was detected in food samples with an average of 2.1 log CFU/g. E. coli was detected only in raw materials, and S. aureus was positive in raw materials as well as environmental swab samples. Other foodborne pathogens were not detected in all samples. The entire B. cereus isolates possessed at least one of the diarrheal toxin genes (hblACD, nheABC, entFM, and cytK enterotoxin gene). However, ces gene encoding emetic toxin was not detected in B. cereus isolates. S. aureus isolates (n=16) contained at least one or more of the tested enterotoxin genes, except for tst gene. For E. coli and S. aureus, 92.7% and 37.5% of the isolates were susceptible against 16 and 19 antimicrobials, respectively. The analyzed microbial hazards could provide useful information for quantitative microbial risk assessment and food safety management system to control foodborne illness outbreaks in food service establishments.

Neonatal Sepsis and Antimicrobial Susceptibilities in the Neonatal Intensive Care Unit and Nursery (신생아 패혈증의 원인 및 항생제 감수성)

  • Moon, Jin Hwa;Oh, Sung Hee;Kim, Hak Won;Moon, Su Jee;Choi, Tae Yeol
    • Pediatric Infection and Vaccine
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    • v.9 no.2
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    • pp.163-174
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    • 2002
  • Background : To delineate the changes in the causative agents of neonatal sepsis and their antimicrobial susceptibilities in the neonatal intensive care unit and nursery of Hanyang University Hospital during the past 10 years. Methods : Hospital records of 15,144 patients hospitalized at the NICU and nursery of Hanyang University Hospital from 1989 to 1998 were reviewed and neonates diagnosed of neonatal sepsis were sorted and included in the study. The study period was divided into Period A(the first 5 years) and Period B(the second 5 years) to analyse causative agents and their antimicrobial susceptibilities. Results : Neonatal sepsis was diagnosed in 170 patients(1.1%{Period A 1.2%, Period B 1.0%}) among the total of 15,144 inpatients. Two hundred isolates(Period A 109 isolates, Period B 91 isolates) were identified in 186 blood cultures(Period A 99 cultures, Period B 87 cultures) from 170 patients(Period A 91 patients, Period B 79 patients). The average age at the onset of the disease, when the initial blood culture was drawn, was 12.3 days old(Period A 8.8 days, Period B 16.3 days), and the proportion of the early onset disease was 34.7% in Period A and 23.0% in Period B, indicating that neonatal sepsis developed earlier during Period A. Among the isolated organisms including Gram positive bacteria[132(66.0%)], Gram negative bacteria [60(30.0%)], and fungi[8(4.0%)], coagulase negative Staphylococcus(CNS) was the most common organism(69/34.5%), followed by Staphylococcus aureus(36/18.0%), Klebsiella pneumoniae(17/8.5%), Enterococcus(12/6.0%), Enterobacter cloacae(8/4.0%), Escherichia coli(6/3.0%), and Pseudomonas aeruginosae(5/2.5%). The isolated fungi were Candida parapsilosis, Candida albicans, and Trichosporon pullulans. CNS, S. aureus and Acinetobacter baumannii were isolated more frequently in Period A compared to Period B. Antimicrobial susceptibilities of CNS and S. aureus to methicillin and the first generation cephalo sporins were decreased in Period B compare to Period A, those to aminoglycosides were increased in Period B, and vancomycin resistant strains were not identified. K. pneumoniae, Enterococcus, E. coli, and P. aeruginosa were isolated less frequently in Period B, compared to Period A. For K. pneumoniae, antimicrobial susceptibilities to the first generation cephalosporins were low in both Periods A and B, those to tobramycin and gentamicin were increased in Period B, and those to amikacin, ceftriaxone, and trimethoprim-sulfamethoxazole were high in both Periods A and B. Antimicrobial susceptibilities of Enterococcous to ampicillin, penicillin, and the first generation cephalosporins were decreased in Period B, but vancomycin resistant strains were not identified. Conclusion : The occurrence rate of neonatal sepsis during the past 10 years in the NICU and nursery of the Hanyang University hospital was 1.1%, and the most common causitive agents were CNS and S. aureus, to which the antimicrobial susceptibilities to the first line drugs decreased in the later half of the study period with no vancomycin resistant isolates identified. Group B Streptococcus known to be the most common agent causing neonatal sepsis was not identified, and K. pneumoniae was isolated more commonly during the later half of the study period without decreased antimicrobial susceptibilities.

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Prevalence of Drug-resistances in Patients with Pulmonary Tuberculosis and Its Association with Clinical Characteristics at One Tertiary Referral Hospital in Pusan, Korea (부산지역 한 3차 병원으로 내원한 폐결핵 환자에서 약제 내성률과 예측인자간의 연관성)

  • Son, Choon-Hee;Yang, Doo-Kyung;Rho, Mee-Sook;Jeong, Jin-Sook;Lee, Hyuck;Lee, Ki-Nam;Choi, Pil-Jo;Lee, Soo-Keol;Chang, Kwang-Yul;Choi, Ik-Soo
    • Tuberculosis and Respiratory Diseases
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    • v.51 no.5
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    • pp.416-425
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    • 2001
  • Background : The incidence of drug-resistant tuberculosis has recently decreased in Korea. However, it is still one of the major obstacles in treating pulmonary tuberculosis. This study was performed to determine the prevalence and clinical characteristics associated with drug-resistance in pulmonary tuberculosis at the tertiary referral hospital in Pusan, Korea. Methods : The medical records of 138 patients, who had been diagnosed as active pulmonary tuberculosis were retrospectively reviewed, and results of drug susceptibility from May 1997 to June 2000. The relationships among those with a history of previous tuberculosis treatment, the extent of lung involvement, the presence of cavities on the initial chest X-ray films and patterns of drug resistance were analyzed. Results : The total number of patients who had drug resistance to at least one drug was 55(39.9%). Among them 34(24.6%) had resistance to isoniazid(INH) and rifampin(RFP). There was drug resistance in 20(22%) of 91 patients without previous tuberculosis therapy, and among them 9(9.9%) were multi-drug resistant. Thirty-two(74.5%) out of 47 patients with previous therapy were drug-resistant and 25(53.2%) were multidrug resistant. For all 138 patients, resistance to INH was the most common(34.1%), followed by RFP(26.1%) and ethambutol(EMB)(14.5%). Drug resistance to INH, RFP, PZA and streptomycin(SM) were independently associated with a history of previous treatment(odds ratio; 9.43, 9.09, 8.93 and 21.6 respectively, p<0.01). The extent of lung involvement on the chest films was significantly associated with the drug resistance to INH and RFP(odds ratio; 2.12 and 2.40 respectively, p<0.01). The prevalence of drug resistance to RFP, INH and RFP was significantly more common in patients with a cavitary lesion on the chest films by multivariate analysis(odds ratio; 4.17 and 4.81 respectively, p<0.05). Conclusion : This study revealed that patients with a prior treatment history for pulmonary tuberculosis, and the presence of a cavitary lesion on chest films had a higher prevalence of anti-tuberculosis drug resistance. A very careful clinical and microbiological examination is needed for patients with such characteristics.

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A Natural L-Arginine Analog, L-Canavanine-Induced Apoptosis is Suppressed by Protein Tyrosine Kinase p56lck in Human Acute Leukemia Jurkat T Cells (인체 급성백혈병 Jurkat T 세포에 있어서 L-canavanine에 의해 유도되는 세포자살기전에 미치는 단백질 티로신 키나아제 p56lck의 저해 효과)

  • Park, Hae-Sun;Jun, Do-Youn;Woo, Hyun-Ju;Rue, Seok-Woo;Kim, Sang-Kook;Kim, Kyung-Min;Park, Wan;Moon, Byung-Jo;Kim, Young-Ho
    • Journal of Life Science
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    • v.19 no.11
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    • pp.1529-1537
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    • 2009
  • To elucidate further the antitumor effects of a natural L-arginine analogue, L-canavanine, the mechanism underlying apoptogenic activity of L-canavanine and its modulation by protein tyrosine kinase $p56^{lck}$ was investigated in human Jurkat T cells. When the cells were treated with 1.25 to 2.5 mM L-canavanine for 36 h, several apoptotic events including mitochondrial membrane potential (${\Delta\Psi}m$) loss, activation of caspase-9, -3, -8, and -7, poly (ADP-ribose) polymerase (PARP) degradation, and DNA fragmentation were induced without alteration in the levels of Fas or FasL. These apoptotic changes were more significant in $p56^{lck}$-deficient Jurkat clone JCaM1.6 than in $p56^{lck}$-positive Jurkat clone E6.1. The L-canavanine-induced apoptosis observed in $p56^{lck}$-deficient JCaM1.6 cells was significantly reduced by introducing $p56^{lck}$ gene into JCaM1.6 cells by stable transfection. Treatment of JCaM1.6/lck cells with L-canavanine caused a transient 1.6-fold increase in the kinase activity of $p56^{lck}$. Both FADD-positive wild-type Jurkat T cell clone A3 and FADD-deficient Jurkat T cell clone I2.1 exhibited a similar susceptibility to the cytotoxicity of L-canavanine, excluding involvement of Fas/FasL system in triggering L-canavanine-induced apoptosis. The L-canavanine-induced apoptotic sub-$G_1$ peak and activation of caspase-3, -8, and -7 were abrogated by pan-caspase inhibitor (z-VAD-fmk), whereas L-canavanine-induced activation of caspase-9 was not affected. These results demonstrated that L-canavanine caused apoptosis of Jurkat T cells via the loss of ${\Delta\Psi}m$, and the activation of caspase-9, -3, -8, and -7, leading to PARP degradation, and that the $p56^{lck}$ kinase attenuated the ${\Delta\Psi}m$ loss and activation of caspases, and thus contributed as a negative regulator to L-canavanine-induced apoptosis.

A Multicenter, Randomized, Open, Comparative Study for the Efficacy and Safety of Oral Moxifloxacin 400 mg Once a Day and Clarithromycin 500 mg Twice Daily in Korean Patients with Acute Exacerbations of Chronic Bronchitis (한국인의 만성 기관지염의 급성 악화 환자를 대상으로 한 Moxifloxacin 400mg 1 일 1회 요법과 Clarithromycin 500mg 1일 2회 요법의 치료효과 및 안전성 비교)

  • Kim, Seung-Joon;Kim, Seok-Chan;Lee, Sook-Young;Yoon, Hyeong-Kyu;Kim, Tae-Yon;Kim, Young-Kyoon;Song, Jeong-Sup;Park, Sung-Hak;Kim, Ho-Joong;Chung, Man-Pyo;Suh, Gee-Young;Kwon, O-Jung;Lee, Shin -Hyung;Kang, Kyung-Ho;Lee, Eh-Hyung;Hwang, Sung-Chul;Han, Myung-Ho
    • Tuberculosis and Respiratory Diseases
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    • v.49 no.6
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    • pp.740-751
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    • 2000
  • Background : Moxifloxacin is a newly developed drug which is more potent and safe compared to previous fluoroquinolones. This drug effectively eradicates organisms such as beta-lactamase-producing or other resistant bacteria. Moxifloxacin is known to be effective in treating respiratory infections such as Streptococcus pneumoniae, Haemophilus influenzae, Moraxella catarrhalis, Chlamydia pneumoniaeme, Legionella spp. and Mycoplasma pneumoniae. Methods : In a multicenter, randomized, open, comparative study, the efficacy and safety of oral moxifloxacin taken 400 mg once a day and clarithromycin taken 500 mg twice daily for 7 days were compared for the treatment of Korean patients with acute exacerbations of chronic bronchitis. Results : A total of 170 patients were enrolled, and they were divided into two groups: 87 in the moxifloxacin group and 83 in the clarithromycin group. Of those enrolled, 76 (35 for bacteriologic efficacy) in the moxifloxacin group and 77 (31 for bacteriologic efficacy) in the clarithromycin group were included in the efficacy analysis. All were included in the safety analysis. Clinical success was noted in 70 (92.1%) of 76 moxifloxacin-treated patients and 71 (92.2%) of 77 clarithromycin-treated patients. Bacteriologic success rate seemed to be higher in moxifloxacin group (73.5%) than in clarithromycin group (54.8%), but statistically insignificant (p=0.098). Drug susceptibility among organisms initially isolated was higher in moxifloxacin group on Streptococcus pneumoniae, Pseudomonas aeruginosa, Klebsiella pneumoniae (p<0.001). Adverse events were reported by 12.8% of 86 patients receiving moxifloxacin and 21.7% of 83 patients receiving clarithromycin. Headache (4.7% vs 4.8%, moxifloxacin group vs clarithromycin group, respectively) and indigestion (2.3% vs 6.0%, moxifloxacin group vs clarithromycin group, respectively) were the most frequent side effects in the two groups. Conclusion : This study demonstrated that for the treatment of acute exacerbations of chronic bronchitis a 7-day course of moxifloxacin 400 mg od was clinically equivalent and microbiologically superior to clarithromycin 500 mg bid.

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Studies on the Occurrence, Host Range, Transmission, and Control of Rice Stripe Disease in Korea (한국에서의 벼 줄무늬잎마름병의 발생, 피해, 기주범위, 전염 및 방제에 관한 연구)

  • Chung Bong Jo
    • Korean journal of applied entomology
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    • v.13 no.4 s.21
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    • pp.181-204
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    • 1974
  • The study has been carried out to investigate the occurrence, damage, host range, transmission and control of rice stripe virus in Korea since 1965. 1 Disease occur「once and damage : The virus infection during the seedling stage ranged from 1.3 to $8\%$. More symptom expression was found in regrowth of clipped rice than infected intact plants, and the greater infection took place in early seasonal culture than in ordinary seasonal culture. A higher incidence of the disease was found on the rows close to the bank, and gradually decreased toward the centre of the rice paddy. Disease occurrence and plant maturity was highly correlated in that the most japonica rice types were diseased when they were inoculated within 3 to 7 leaf stage, and$50\%$, $20\%$ and no diseaseb were found if they were inoculated at 9, 11 and 13 leaf stages, respectively. Symptom expression required 7-15 days when the plants were inoculated during 3-7 leaf stages, while it was 15-30days in the plants inoculated during 9-15 leaf stages. On Tongil variety the per cent disease was relatively higher when the plants were infected within 1.5-5 leaf stages than those at 9 leaf stage, and no disease was found on the plants infected after 15 leaf stage. The disease resulted in lowered growth rates, maturity and sterility of Tongil variety although the variety is known as tolerant to the virus. 2. Host range: Thirty five species of crops, pasture grasses and weeds were tested for their susceptibility to the virus. Twenty one out of 35 species tested were found to be susceptible. and 3 of them, Cyperus amuricus Maximowics var. laxus, Purcereus sanguinolentus Nees and Eriocaulon robustius Makino, were found as new hosts of the virus. 3. Transmission: The vector of the virus, Laodelphax striatellus, produces 5 generations a year. The peak of second generation adults occurred at June 20th and those of third was at about July 30th in Suweon area. In Jinju area the peak of second generation adult proceeded the peak at Suweon by 5-7 days. The peaak of third generation adult was higher than the second at Jinju, but at Suweon the reverse was true. The occurrence of viruliferous Laodelphax striatellus was 10-15, 9, 17, 8 and about $10\%$ from overwintered nymph, 1st generation nymph, 2nd generation adult, End generation nymph and the remaining generations, respectively. More viruliferous L. striatellus were found in the southern area than in the central area of Korea. The occurrence of viruliferous L. striatellus depended on the circumstances of the year. The per cent viruliferous vectors gin 2nd and 3rd generation adult, however, was consistantly higher than that of other generations. Matings of viruliferous L. striatellus resulted in $90\%$ viruliferous progenies, and the 3rd, 4th and 5th instars of the vector had higher infectiviey than the rest of the vector stages. The virus acquisition rate of non-viruliferous L. striatellus was $7-9\%$, These viruliferous L. striatellus, however, could not transmit the virus for more than 3 serial times. The optimum temperature for the transmission of the viru3 was $25-30^{\circ}C$, while rare transmission occurred when the temperature was below $15^{\circ}C$. The per cent of L. striatellus parasitization by Haplogonatopus atratus were $5-48\%$ during the period from June to the end of August, and the maximum parasitization was $32-48\%$ at around July 10. 4. Control: 1) Cultural practices; The deeper the depth of transplanting more the disease occurrence was found. The higher infection rate, $1.5-3.5\%$, was observed during the late stages of seedling beds, and the rate became lower, $1.0-2.0\%$, in the early period of paddy field in southern area. Early transplanting resulted in more infection than early seasonal culture, and the ordinary seasonal culture showed the lowest infection. The disease also was favored by earlier transplanting even under tile ordinary seasonal culture. The higher the nitrogen fertilizer level the more the disease occurrence was found in the paddy field. 2) Resistant varieties; Tongil varieties shelved the resistant reaction to the virus in greenhouse tests. In the tests for resistance on 955 varieties most japonica types shelved susceptible reactions, while the resistant varieties were found mostly from introduced varietal groups. 3) Chemical control; Earlier applications of chemicals, Disyston and Diazinon, showed better results when the test was made 4 days after inoculation in the greenhouse even though none of the insecticides shelved the complete control of the disease. Three serial applications of chemicals on June 14, June 20 and June 28 showed bettor results than one or two applications at any other dates under field conditions.

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