• International Journal of Industrial Entomology and Biomaterials
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• v.30 no.2
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• pp.40-44
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• 2015

To investigate whether Serratia marcescens (Enterobacteriales: Enterobacteriaceae) isolated from Protaetia brevitarsis seulensis (Coleoptera: Cetoniidae) acts as an opportunistic bacterium in peroral infection, the primary entomopathogenic bacteria Bacillus thuringiensis (Bacillales: Bacillaceae) and Paenibacillus popilliae (Eubacteriales: Bacillaceae) were added to sawdust to perform a bioassay experiment. We found that peroral infection caused by S. marcescens could be fatal beyond a concentration of $4{\times}10^8pfu/mL$ in $2^{nd}$ stage P. b. seulensis larvae and at $6{\times}10^8pfu/mL$ in $3^{rd}$ stage P. b. seulensis larvae. In particular, mortality resulting from a combination of P. popilliae and S. marcescens was markedly increased in $2^{nd}$ stage P. b. seulensis larvae. Therefore, we confirmed that mortality was increased when S. marcescens was infected together with other entomopathogenic bacteria, and that peroral infection itself can be fatal beyond certain concentrations.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.35 no.5
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• pp.455-461
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• 2002

limiting nutrients for phytoplankton were determined by dissored inorganic nitrogen/phosphorous (DIN/DIP) in situ and algal bioassay experiment in the Seomjin River estuary during a study period from March 1999 to October 2001. DIN/DIP ranged from 14.7 to 681.1 during the study period. DIN/DIP was over 16 at the upper and middle estuarine region where salinity was lower than 25 psu and chlorophyll a concentration was high, probably indicating P-limitation in this region while the ratio was less than 16 at the high saline (> 25 psu) region, reflecting the supply of DIP from Gwangyang Bay and thereby indicating N-limitation at the lower estuarine region. These results suggested that the spatial distribution of DIN/DIP in the study region was controlled by the high supply of phosphate from Gwangyang Bay, the low input from Seomjin River and the active uptake by phytoplankton within the estuarine system. The bioassay experiments using Skeletonema costatum, Thalaasiosira rotula and in situ phytoplankton assemblage displayed relatively higher growth of phytoplankton in the P-added culture media, indicating P-limitation. This result was well consistent with the spatial distribution of inorganic nutrients. S. costatum showed a rapid adaptation to the low salinity compared to other phytoplankton species. This phenomenon seemed to account for the strong (> $90\%$ in total cell number) S. costatum bloom in autumn in this estuary. Moreover, although phytoplankton growth rate was higher in the P-added culture media at the end of culture experiment of in situ phytoplankton, the fast growth in the trace metal-added media at the beginning of the experiment suggested a possibility of limitation by other micro-nutrients such as trace metal and vitamin etc.

• The Plant Pathology Journal
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• v.18 no.6
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• pp.338-341
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• 2002

The potato scab is caused by several species of Streptomyces. Among these species, only pathogenic strains were found to produce thaxtomin A characterized by necrotic bioassay and HPLC. In this study, identification of the pathogenic strains of Streptomyces was performed through the polymerase chain reaction (PCR) by using specific pathogenicity primer sets derived from the nec1 gene sequences of Streptomyces scabies. The expected PCR products were obtained approximately 580 bp and confirmed by sequencing. This PCR technique can be used effectively to identify the pathogenic Streptomyces species, that cause scab on potato tubers.

• The Korean Journal of Physiology and Pharmacology
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• v.3 no.4
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• pp.393-404
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• 1999

We have reported that hypoxia stimulates EDRF(s) release from endothelial cells and the release may be augmented by previous hypoxia. As a mechanism, it was hypothesized that reoxygenation can stimulate EDRF(s) release from endothelial cells and we tested the hypothesis via bioassay experiment. In the bioassay experiment, rabbit aorta with endothelium was used as EDRF donor vessel and rabbit carotid artery without endothelium as a bioassay test ring. The test ring was contracted by prostaglandin $F_{2a}\;(3{\times}10^{-6}\;M)$ which was added to the solution perfusing through the aorta. Hypoxia was evoked by switching the solution aerated with 95% $O_2/5%\;CO_2$ mixed gas to one aerated with 95% $O_2/5%\;CO_2$ mixed gas. Hypoxia/reoxygenation were interexchanged at intervals of 2 minutes (intermittent hypoxia). In some experiments, endothelial cells were exposed to 10-minute hypoxia (continuous hypoxia) and then exposed to reoxygenation and intermittent hypoxia. In other experiments, the duration of reoxygenation was extended from 2 minutes to 5 minutes. When the donor aorta was exposed to intermittent hypoxia, hypoxia stimulated EDRF(s) release from endothelial cells and the hypoxia-induced EDRF(s) release was augmented by previous hypoxia/reoxygenation. When the donor aorta was exposed to continuous hypoxia, there was no increase of hypoxia-induced EDRF(s) release during hypoxia. But, after the donor aorta was exposed to reoxygenation, hypoxia-induced EDRF(s) release was markedly increased. When the donor aorta was pretreated with nitro-L-arginine $(10^{-5}$ M for 30 minutes), the initial hypoxia-induced EDRF(s) release was almost completely abolished, but the mechanism for EDRF(s) release by the reoxygenation and subsequent hypoxia still remained to be clarified. TEA also blocked incompletely hypoxia-induced and hypoxia/reoxygenation-induced EDRF(s) release. EDRF(s) release by repetitive hypoxia and reoxygenation was completely blocked by the combined treatment with nitro-L-arginine and TEA. Cytochrome P450 blocker, SKF-525A, inhibited the EDRF(s) release reversibly and endothelin antgonists, BQ 123 and BQ 788, had no effect on the release of endothelium-derived vasoactive factors. Superoxide dismutase (SOD) and catalase inhibited the EDRF(s) release from endothelial cells. From these data, it could be concluded that reoxygenation stimulates EDRF(s) release and hypoxia/reoxygenation can release not only NO but also another EDRF from endothelial cells by the production of oxygen free radicals.

• The Plant Pathology Journal
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• v.20 no.1
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• pp.52-57
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• 2004

Sclerotinia sp. (isolate BWC98-105) causes stem blight and root rot in Leghum sp., and is presently being evaluated as a potential mycoherbicide for the control of Trifoliorium repens. Bioassays have shown that Sclerotinia sp. produces phytotoxic substance which is biologically active against T. repens. Two biologically active compounds, designated as compoundsI and II, were produced in vitro from the culture filtrate of BWC98-105 isolate Sclerotium sp. Compounds I and II were purified by means of liquid-liquid extraction and $C_{18}$ open column chromatography (300 ${\times}$ 30 mm, i.d). To determine the purity, the purified compounds were analyzed by RP-HPLC. The analytical RP-HPLC column was a TOSOH ODS-120T (150 ${\times}$ 4.6 mm i.d, Japan), of which the flow rate was set at 0.7 mL/min using the linear gradient solvent system initiated with 15 % methanol to 85 % methanol for 50 min with monitoring at 254 nm. Under these RP-HPLC conditions, compounds I and II eluted at 3.49 and 4.13 min, respectively. Compound II was found to be most potent and host specific. However, compound I had a unique antibiotic activity against phytopathogenic bacteria like bacterial leaf blight (Xanthomonas oryzae) on rice, where it played a less important role in producing toxicity on T. repens. No toxin activity was detected in the water fraction after partitioning with several organic solvents. However, toxin activity was detected in the ethyl acetate and butanol fractions. In the leaf bioassay using compound II, the disease first appeared within 4-5 h as water soaked rot, which subsequently developed into well-defined blight affecting the whole plant.

• Journal of Environmental Science International
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• v.10 no.4
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• pp.293-298
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• 2001

The toxicity values heavy metals were evaluated by immobilization and chronic reproduction impairment tests, using Daphnia magna. Acute tests were evaluated by the inhibition of their mobilization after 24hrs without food addition. The tests of reproductive impairment were investigated for 21 days by food addition and exchange or water. The effect of each concentration was assessed by Probit analysis and t-test. The results obtained from this study were as follows : 1) The change of pH and DO was not significant in the acute tests, while, in the reproductive tests, pH was increased by 0.3~1.4 and DO also increased. 2) The $E_iC_{50}$ values of immobilization to Daphnia magna in artificial fresh water were $0.030mg/{\ell}(Cu),\;0.054mg/{\ell}(Cd),\;0.12mg/{\ell};(Cr),\;0.74mg/{\ell}(Pb),\;3.4mg/ {\ell}(As)$ and the $NOE_iC$ values were $0.010mg/{\ell}(Cu),\;0.018mg/{\ell}(Cd),\;0.010mg/{\ell}(Cr),\;0.10mg/{\ell}(Pb),\;and\;$1.8mg/{\ell}(As)$. 3) The $E_rC_{50}$ values of reproductive impairment to Daphnia magna were $13.8\mu\textrm{g}/{\ell}(Cu),\;2.9\mu\textrm{g}/{\ell}(Cd),\;15.5\mu\textrm{g}/{\ell}(Cr),\;61.7\mu\textrm{g}/{\ell}(Pb),\;759\mu\textrm{g}/{\ell}(As)$, and $NOE_rC$ values were $0.95\mu\textrm{g}/{\ell}(Cu),\;$0.54\mu\textrm{g}/{\ell}(Cd),\;1.2\mu\textrm{g}/{\ell}(Cd),\;$7.4\mu\textrm{g}/{\ell}(Pb),\;110mu\textrm{g}/{\ell}(As)$. The results of tests using OECD artificial culture water were more sensitive than natural water for culturing. The presented data show that an artificial culture water is suitable in the experiment of bioassay for assessing the toxicity of marterials.

• The Korean Journal of Physiology
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• v.27 no.2
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• pp.199-207
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• 1993

To study the underlying mechanism through which the endothelium-dependent relaxation is inhibited by blocking the $Na^+\;-K^+$ pump, the effects of $Na^+\;-K^+$ pump blockade on the release of EDRF and its relaxing activity were examined, using organ bath study, bioassay technique, and cGMP measurement. Endothelium-dependent relaxation was attenuated by blocking the $Na^+\;-K^+$ pump in the vascular ring with intact endothelium. In bioassay experiment EDRF release was decreased with the blockade of the $Na^+\;-K^+$ pump in the EDRF donor strip. Endothelium-dependent increase of cGMP level was suppressed by inhibiting the $Na^+\;-K^+$ pump in the test strips. The magnitude of relaxation of test strip which was induced by the perfusate that had passed through the EDRF donor strip was decreased with the blockade of the $Na^+\;-K^+$ pump in the test strip. Therefore, it could be suggested that the attenuation of endothelium-dependent relaxation caused by inhibiting $Na^+\;-K^+$ pump activity is due to both the decreased release of EDRF from endothelial cells and the decreased sensitivity of the smooth muscle cells to EDRF.

• Korean Journal of Veterinary Research
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• v.34 no.3
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• pp.609-617
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• 1994

This study was performed for assessing carcinogenicity of Folpet using medium-term carcinogenicity bioassay. Sprague-Dawley rats aged six weeks divided into four grout's and were initially given an intraperitoneal injection of diethylnirosamine at 200mg/kg body weight. Two weeks later, group 1(negative control) was treated with basal diet. A Folpet was given per oral administration to group 2(100 ppm) and goup 3(1,000 ppm). Group 4 was fed on water containing 0.05% phenobarbital sodium as a promtor for six weeks. At three weeks after beginning of the experiment, partial hepatectomy was performed in all rats. The tumor-promoting effects were examined by the numbers and areas per $cm^2$ of induced glutathion S-tranferase placetal form(GST-P) positive foci in liver, and silver stained nucleolar organizer regions(AgNORs) which have recently introduced as one of the indicators for the cell proliferative activity. As the results, Folpet didn't have tumor-promoting effects on GST-P positive foci developement and AgNORs during promoting stage after initiation, whereas phenobarbital sodium treatment group showed promoting effect. It was concluded that Folpet didn't have promoting effect at 500, 1,000 ppm using this midium-term carcinogenicity bioassay model.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.38 no.2
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• pp.100-105
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• 2005

Two species of fish and five species of marine invertebrate showed different tolerances to the toxicity of composite slag and bituminaus coal. Especially, Hemicentrotus pulcherrimus and young Haliotis discus hannai displayed marked differences in tolerance from. H. pulcherrimus and young H. discus hannai showed lethal effects at higher concentrations than those concentrations of the composite slag in the 1.0 and $0.4\%$ range, respectively. H. pulcherrimus showed no lethal effects at a lower concentration of $1.0\%$ composite slag and some differences in the rate of oxygen consumption with this concentration of composite slag. The lethal effects of bituminous coal on marine and fisheries organisms, even with higher concentrations, were not observed. At a higher concentration than that of 500 mg/L (ppm) of bituminous coal, decrease effects appeared in the rate of oxygen consumption of the experimental organisms. Taking into consideration that the experimental concentration of composite slag and bituminous coal were impracticable in the ocean, the results of this experiment suggest that composite slag and bituminous coal pose no real threat to marine or fisheries organisms.

• Applied Biological Chemistry
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• v.45 no.4
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• pp.185-189
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• 2002

Along with the worldwide rapid increase of the cultivation area and commercial production of genetically modified (GM) crops, the amount of GM grains imported to Korea has also been increasing. Roundup-Ready soybean (RRS) was introduced with 5-enolpyruvyl shikimate-3-photphate synthase (EPSPS) gene derived from Agrobacterium CP4 to confer the resistance to herbicide, glyphosate. In this study, we tried to develop PCR-based analytical method to detection the presence of RRS among non-GM soybeans. In order to detect RRS specifically, oligonucleotide primers were specifically designed based on the nucleotide sequence of EPSPS transgene. Qualitative PCR method was established and its specificity and accuracy were confirmed by analysing the nucleotide sequence of PCR DNA fragments. Bioassay was also conducted by spraying glyphosate at seedling stage. Survived individuals showed obvious resistance to Roundup Ready, however all of non-GM seedlings died in two weeks after spray. Conclusively, the highly selective detection systems for RRS were successfully established by both PCR using specific primers to EPSPS transgene and bioassay using the herbicide resistance of RRS. In addition to, the imported soybean showed to be mixed to several varieties regarding to 100-seed weight and hilum color.