• Journal of Radiation Protection and Research
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• v.32 no.4
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• pp.184-189
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• 2007

In order to investigate the enhancement effects of low dose radiation on biological activation, this study applied low dose X-ray to the whole body of male rats to find out whether hormesis is induced in male germ cells. Total 36 Sprague-Dawley(SD) rats as experimental animal were subdivided into 6 groups(in 6 rats per group) such as control, 10 mGy, 20 mGy, 50 mGy, 100 mGy and 200 mGy radiation group All the groups showed slightly increasing number of sperms per 0.1g semen ($14.216{\times}10^6,\;13.901{\times}10^6,\;14.153{\times}10^6,\;13.831{\times}10^6,\;14.137{\times}10^6,\;14.677{\times}10^6$ respectively), and the motility of sperms amounted to 50.9%, 49.5%, 55.1%, 54.3%, 48.0% and 52.2% respectively. Particularly, compared to the control, the other 5 groups showed higher male hormone level, and the microscopic observations of testicle tissues showed no vacuolization in seminiferous tubules and testis cells. In the results of this experiment, no harmful effect was observed on Sprague-Dawley (SD) rats for which the dose of radiation was controlled as regulated legally by the Ministry of Science and Technology and the Ministry of Health and Welfare. However, as these results were obtained from a limited number of animals, we cannot maintain that the same effect will be observed in the human body. Therefore, there should be further research on the effect on other animals and ultimately on the human body.

• Korean Journal of Medicinal Crop Science
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• v.10 no.3
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• pp.155-161
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• 2002

Using semi-selective (SS-) and selective (Jee-) medium, we identified the pathogens isolated from the symptomatic plants and soils collected from different locations, such as Suwon, Andong, and Youngju, as P. drechsleri, which is Phytophthora root rot causal agent of A. macrocephala. At $25^{\circ}C$, these isolates were grown faster on 10% V8A (V8 juice agar) medium than on PDA (potato dextrose agar) with hyphal swelling, but no growing was observed at below $5^{\circ}C$ and over $40^{\circ}C$. In order to identify the pathogenicity of each isolate, seedlings of A. macrocephala were inoculated with mycelium -zoospore suspended inoculum, which was prepared by culturing on 10% V8A medium and homogenizing in distilled water. By this method, wide ranges of pathogenicity were observed as follows; $5.0%{\sim}26.4%$ of disease severities concerning the lesion areas of the top plants and $23.5%{\sim}72.2%$ of disease incidences. Therefore, this was considered as a efficient method to identify the pathogenicity of P. drechsleri in large scale screening. P-A200073, isolated from soils in Andong, and P-9755, from the root of symptomatic plant of A. macrocephala in Suwon, showed the highest degree of pathogenicity to the seedlings. By these isolates, lesion areas and disease incidences of the inoculated seedlings were occurred $26.4%{\sim}63.2%$ and $25.1%{\sim}72.2%$, respectively. However, no symptoms were observed in uninoculated control. Same pathogens were reisolated from roots and lower stems of the inoculated plants, but not from leaves.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.16 no.1
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• pp.27-38
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• 2011

The distributions of phytoplankton assemblages and environmental factors in Jinhae Bay and their relationships were investigated to estimate the potential limiting nutrient for phytoplankton growth and community structure. In situ algal bioassay experiments were also conducted to assess the species-specific characteristics in phytoplankton responses under different nutrient conditions (control, N(+) and P(+) treatment). During the study periods, bacillariophyceae and cryptophyceae occupied more than 90% of total phytoplankton assemblages. Phytoplankton standing crops in the inner part of Masan Bay were higher than that of Jinhae Bay. The DIN:DIP ratio, pH and transparency showed the significant positive correlation with phytoplankton biomass. According to cluster and multidimensiolnal scaling (MDS) analysis based on phytoplankton community data from each station, the bay was divided into three groups. The first group included stations from the south-western part of Jinhae bay where cryptophyta species were dominated. The second group was distinguished from inner stations in Masan Bay. These stations showed low transpancy and high DIN:DIP ratio. The other cluster included the stations from the eastern part and central part of Jinhae Bay, which was characterized by the high DSi:DIP ratio and dominant of diatom species. Phosphorous (P) was limited in Masan Bay due to significantly increases in the phytoplankton abundances. Based on stoichiometric limitation and algal bio-assay in Jinhae Bay, nitrogen (N) was a major limiting factor for phytoplankton production. However, silicate (Si) was not considered as limiting factor, since Si/DIN and Si/P ratio and absolute concentration of nutrient did not create any potential stoichiometric limitation in the bay. This implies that high Si availability in winter season contributes favorably to the maintenances of diatom species.

• Weed & Turfgrass Science
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• v.1 no.4
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• pp.44-49
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• 2012

The objective of this study was to know the herbicidal activity of the essential oil from amyris (Amyris balsamifera). In a seed bioassay experiment, the amyris essential oil inhibited the growth of rapeseed (Brassica napus) by fifty percent at 8.8 ${\mu}g\;g^{-1}$. And in a greenhouse experiment, sorghum, barnyard grass and Indian jointvetch, which was applied in above-ground parts, with the amyris essential oil at 4,000 ${\mu}g\;ml^{-1}$ showed visual injuries of 90, 70, and 70, respectively (0, no damage; 100, total damage). However, soil application of the essential oil did not show such herbicidal injuries. In a field experiment, foliar application of the amyris essential oil at 5% controlled effectively weeds such as barnyardgrass, shepherd's purse, and clover in 24 hours. Our results indicated that the amyris essential oil had herbicidal activity. To understand the composition of the amyris essential oil, the oil was analyzed by gas chromatography-mass spectometry with solid-phase micro-extraction apparatus. There were 15 organic chemicals in the oil and the major constituents were calarene, elemol, ${\gamma}$-eudesmol, curcumene, ${\beta}$-sesquiphellandrene, zingiberene, selina-3,7(11)-diene, 1,3-diisopropenyl-6-methyl-cyclohexene, ${\beta}$-bisabolene, and ${\beta}$-maaliene. Overall results suggest that the amyris essential oil had a herbicidal activity with fast, contact, and non-selective mechanism.

• Environmental Engineering Research
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• v.12 no.1
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• pp.16-20
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• 2007

Toxicity of metal plating wastewater was evaluated by using acute toxicity tests on Daphnia magna. To identify toxicants of metal plating wastewater, several manipulations such as solid phase extraction (SPE), ion exchange and graduated pH adjustment were used. The SPE test had no significant effect on baseline toxicity, suggesting absence of toxic non-polar organics in metal plating wastewater. However, anion exchange largely decreased the baseline toxicity by 88%, indicating the causative toxicants were inorganic anions. Considering high concentration of chromium in metal plating wastewater, it is thought the anion is Cr(VI) species. Graduated pH test showing independence of the toxicity on pH change strongly supports this assumption. However, as revealed by toxicity confirmation experiment, the initial toxicity of metal plating wastewater (24-h TU=435) was not explained only by Cr(VI) (24-h TU = 725 at $280\;mg\;L^{-1}$). Addition of nickel($29.5\;mg\;L^{-1}$) and copper ($26.5\;mg\;L^{-1}$) largely decreased the chromium toxicity up to 417 TU, indicating antagonistic interaction between heavy metals. This heavy metal interaction was successfully predicted by an equation of 24-h $TU\;=\;3.67\;{\times}\;\ln([Cu]\;+\;[Ni])\;+\;79.44$ at a fixed concentration of chromium.

• Toxicological Research
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• v.34 no.4
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• pp.291-296
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• 2018

Chemical carcinogenesis is a multistep process. Genotoxic carcinogens, which are DNA-reactive, induce DNA adduct formation and genetic alterations in target cells, thereby generating mutated cells (initiation). Subsequently, preneoplastic lesions appear through clonal proliferation of the mutated cells and transform into tumors (promotion and progression). Many factors may influence these processes in a dose-dependent manner. Therefore, quantitative analysis plays an important role in studies on the carcinogenic threshold of genotoxic carcinogens. Herein, we present data on the relationship between key carcinogenic events and their deriving point of departure (PoD). Their PoDs were also compared to those of the carcinogenesis pathway. In an experiment, the liver of rats exposed to 2-amino-3,8-dimethylimidazo-(4,5-f)quinoxaline (MeIQx) was examined to determine the formation of MeIQx-DNA adducts, generation of mutations at LacI transgene, and induction of preneoplastic glutathione S-transferase placental form (GST-P)-positive foci and tumors (benign and malignant). The PoDs of the above key events in the carcinogenicity of MeIQx were increased as the carcinogenesis advanced; however, these PoDs were lower than those of tumor induction. Thus, the order of key events during tumor induction in the liver was as follows: formation of DNA adducts ${\ll}$ Mutations ${\ll}$ GST-positive foci (preneoplasia) ${\ll}$ Tumor (adenoma and carcinoma). We also obtained similar data on the genotoxic and carcinogenic PoDs of other hepatocarcinogens, such as 2-amino-3,8-dimethylimidazo(4,5-f)quinoline. These results contribute to elucidating the existence of a genotoxic and carcinogenic threshold.

• International Journal of Industrial Entomology and Biomaterials
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• v.13 no.1
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• pp.15-22
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• 2006

An experiment was conducted to study the efficiency of cyanobacterial biofertilizer (CBB) with chemical (NPK) fertilizer on quantitative and qualitative characters of mulberry variety Kanva-2. Their influences on silkworm growth and cocoon characters were also studied. Ten different CBB and NPK fertilizer treatments were given to 5000 plants of established mulberry garden. Treatments were of four types viz., (i) T1 to T7: single and combination dose of CBB+50% NPK (ii) T8: combination dose of CBB + 25%NPK, (iii) T9: CBB only and (iv) T10: control-l00% NPK. Soil pH decreased and nutrients status increased in CBB (T1- T9) treated plots. Average of ten crops data on quantitative traits revealed that T7 (CBB [N. muscorum (1.0 g), A. variahilis (1.0) and S. millei (1.0 g)] + 50% NPK) was very effective in improving growth parameters. Leaf yield was also found high in treatment T7 (32.12 tons/ha/yr.) followed by T10 (31.17 tons/ha/yr.) and T8 (27.67 tons/ha/yr.). Leaf quality characters were found high in T7 and low in T9. Most of the quality traits in T7 are on par with control no. The results revealed that reduction in the dose of chemical fertilizers in T7 did not affect the leaf yield and leaf quality traits of mulberry. This clearly indicates that the efficiency of CBB (T7) provides nitrogen, increases essential nutrients available in soil, maintain soil pH and supply growth substances required for the improvement of leaf yield and leaf quality of mulberry. Bioassay study also revealed no significant difference in silkworm growth and cocoon characters between treatments T7 and T10. Economics calculated revealed that T7 is highly economical and beneficial over T10 by gaining an amount of Rs. 660/-/acre/crop. Thus, treatment T7 containing N. muscorum (1.0 g), A. variahilis (1.0 g) and S. millei (1.0 g) + 50% NPK fertilizers can be recommended to sericulturists mainly to reduce the use of NPK fertilizers, by saving 50% of its cost and to improve soil fertility conditions, which in turn improves leaf yield and quality of mulberry.

• Journal of Microbiology and Biotechnology
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• v.19 no.10
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• pp.1244-1249
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• 2009

Endophytic fungi are known for the production of valuable metabolites, but information on the gibberellin production capacity of this group is limited. We isolated 9 endophytic fungi from the roots of salt-stressed soybean plants and screened them on waito-c rice, in order to identify plant growth promoting fungal strains. The fungal isolate TK-2-4 gave maximum plant length (20.35 cm) promotion in comparison with wild-type Gibberella fujikuroi (19.5 cm). In a separate experiment, bioassay of TK-2-4 promoted plant length and biomass of soybean cultivar Taegwangkong. The TK-2-4 culture filtrate was analyzed for the presence of gibberellins, and it was found that all physiologically active gibberellins, especially $GA_4$ and $GA_7$, were present in higher amounts ($GA_1$, 0.11 ng/ml; $GA_3$, 2.91 ng/ml; $GA_4$, 3.21 ng/ml; and $GA_7$, 1.4 ng/ml) in conjunction with physiologically inactive $GA_9$ (0.05 ng/ml), $GA_{12}$ (0.23 ng/ ml), $GA_{15}$ (0.42 ng/ml), $GA_{19}$ (0.53 ng/ml), and $GA_{20}$ (0.06 ng/ml). The fungal isolate TK-2-4 was later identified as a new strain of Phoma herbarum, through the phylogenetic analysis of 28S rDNA sequence.

• Journal of Chest Surgery
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• v.24 no.3
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• pp.229-244
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• 1991

A bioassay technique and organ bath study were performed to analyze the effects of extracellular $Ca^{2+}$ and $Ca^{2+}$-antagonists on endothelium-derived relaxing factor[s][EDRF] released from the endothelial cells of rabbit aorta. Transverse strips with intact endothelium or damaged endothelium were used for the mechanical contraction experiment using organ bath. Long segment including thoracic and abdominal aorta with endothelium [EDRF donor aorta] was perfused with Tyrode solution which was aerated with 95% $O_2-5%$ $CO_2$ mixed gas and kept at 35oC. The perfusate was bioassayed with a transverse strip of thoracic aorta with damaged endothelium. The test strip was contracted with nor-epinephrine and acetylcholine was used to stimulate the release of EDRF from endothelial cells. The results obtained were as follows; 1] The endothelium-dependent relaxation[EDR] induced by acetylcholine was biphasic; an initial rapid relaxation followed by a slow relaxation. 2] EDR induced by acetylcholine was reduced gradually with the decrease in the concentration of extracellular $Ca^{2+}$. The effect of extracellular $Ca^{2+}$ on EDR was more prominent in the late slow relaxation phase. 3] EDR to acetylcholine was not altered by acute exposure to organic $Ca^{2+}$-antagonists. Pretreatment with verapamil to the EDRF donor aortic segment did not alter the magnitude of EDR. 4] Among the inorganic $Ca^{2+}$-antagonists $Mn^{2+}$ and $Cd^{2+}$ did not inhibit EDR, whereas $Co^{2+}$ and $La^{3+}$ inhibited EDR. 5] The inhibitory response of $Co^{2+}$ to EDR developed when infused directly on the test strip. That of $La^{3+}$, however, was evoked when added to solution perfusing the donor aortic segment. The above results suggest that $Ca^{2+}$-antagonists do not affect EDR and the inhibitory effect of $Ca^{2+}$ results from influencing the action of EDRF on vascular smooth muscle, whereas that of $La^{3+}$ results from its action on the release of EDRF from endothelial cells.

• Journal of the Korean Society of Food Science and Nutrition
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• v.2 no.1
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• pp.23-30
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• 1973

Wistar strain male rats were divided into four different diet groups and the control group was fed on 7-percent casein diet (C), the second with a mixture of 80% of rice and 20% of buckwheat (RW), the third with rice only (R), and the fourth with a mixture of rice and buckwheat of equal nitrogen level (RWS). Each diet group consisted of 6 rats was fed for three weeks by the ad libitum feeding method. The results of the experiment, i.e., the growth gain and change in the level of free amino acids in the plasma and liver determined by the micro-bioassay method were as follows. 1. The group C showed the largest growth gain and the rest did in the order of RW group, R group. and RWS group. 2. Rats fed on diet of high protein score showed high level of free amino acids tryptophan, lysine, and threonine in the plasma and liver except for the case of lysine in the liver. 3. Protein score would be estimated by the level of free amino acids in the liver and plasma.