• Molecules and Cells
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• v.26 no.2
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• pp.171-174
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• 2008

Flavone (2-phenyl chromone) is a well-known plant flavonoid, but its bioactivity has been little explored. Treatment of Caenorhabditis elegans or C. brissage with flavones induced embryonic and larval lethality that was pronounced in early larval stages. This anti-nematodal effect was also observed in the pinewood nematode, B. xylophilus. $LD_{50}$ values were approximately $100{\mu}M$ for both B. xylophilus and C. elegans. Our results indicate that flavone is an active nematicidal compound that should be further investigated with the aim of developing a potent drug against B. xylophilus.

• Molecules and Cells
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• v.19 no.3
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• pp.452-457
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• 2005

The adaptor protein (AP) complexes are involved in membrane transport of many proteins. There are 3 AP complexes in C. elegans unlike mammals that have four. To study the biological functions of the AP-3 complexes of C. elegans, we sought homologues of the mouse and human genes that encode subunits of the AP-3 complexes by screening C. elegans genomic and EST sequences. We identified single copies of homologues of the ${\mu}3$, ${\sigma}3$, ${\beta}3$ and ${\delta}$ genes. The medium chain of AP-3 is encoded by a single gene in C. elegans but two different genes in mammals. Since there are no known mutations in these genes in C. elegans, we performed RNAi to assess their functions in development. RNAi of each of the genes caused embryonic and larval lethal phenotypes. APM-3 is expressed in most cells, particularly strongly in spermatheca and vulva. We conclude that the products of the C. elegans ${\mu}3$, ${\sigma}3$, ${\beta}3$ and d genes are essential for embryogenesis and larval development.

• Bulletin of the Korean Chemical Society
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• v.30 no.2
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• pp.323-326
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• 2009

SR proteins are essential splicing regulators and also modulate alternative splicing events, which function both as redundant and substrate-specific manner. The Drosophila B52/SRp55, a member of the SR protein family, is essential for the fly development in vivo, as deletion of B52 gene results in lethality of animals at the second instar larval stage. Identification of the splicing target genes of B52 thus should be crucial for the understanding of the specific developmental role of B52 in vivo. In this study, we performed whole-genome DNA microarray experiments with a B52- knock-out animal. Analysis of the microarray data not only provided the B52-dependent gene expression signature, but also revealed a larval-stage specific, alternative splicing target gene of B52. Our result thus provides a starting point to understand the essential function of B52 at the organismal level.

• Molecules and Cells
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• v.38 no.3
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• pp.236-242
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• 2015

Intake of caffeine during pregnancy can cause retardation of fetal development. Although the significant influence of caffeine on animal development is widely recognized, much remains unknown about its mode of action because of its pleiotropic effects on living organisms. In the present study, by using Caenorhabditis elegans as a model organism, the effects of caffeine on development were examined. Brood size, embryonic lethality, and percent larval development were investigated, and caffeine was found to inhibit the development of C. elegans at most of the stages in a dosage-dependent fashion. Upon treatment with 30 mM caffeine, the majority ($86.1{\pm}3.4%$) of the L1 larvae were irreversibly arrested without further development. In contrast, many of the late-stage larvae survived and grew to adults when exposed to the same 30 mM caffeine. These results suggest that early-stage larvae are more susceptible to caffeine than later-stage larvae. To understand the metabolic responses to caffeine treatment, the levels of expression of cytochrome P450 (cyp) genes were examined with or without caffeine treatment using comparative microarray, and it was found that the expression of 24 cyp genes was increased by more than 2-fold (p < 0.05). Among them, induction of the cyp-35A gene family was the most prominent. Interestingly, depletion of the cyp-35A family genes one-by-one or in combination through RNA interference resulted in partial rescue from early larval developmental arrest caused by caffeine treatment, suggesting that the high-level induction of cyp-35A family genes can be fatal to the development of early-stage larvae.

• Korean journal of applied entomology
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• v.4
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• pp.67-74
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• 1965

The work on the 'Studies of radiosensitivity' in Korea has been initiated since 1959 by the author at various institutions in home and foreign countries, and more than 20000 of plant materials in 73 varieties and 41 kinds are treated under varied conditions for the studies of radiosensitivity in plants. However, a study of the susceptibility to radiation in insect pests as well as their biological effects has not been previously reported in this country. During the year of 1964 and 1965, near 50000 of insects at the stages of adult, egg, larva and pupa in 14 different kinds are irradiated under acute X and gamma rays to investigate the behavior of growth and lethality after irradiation, and thrir general tolerances to radiations are compared by the kind of insects, stage of growth, radiation sources and exposured dosages. Through the experiments, it is shown that the lethality in most of insects are high as several kilo roentgens above and no significant effects on pupation. emergence, and oviposition in the treated generation at the dose of 3 Kr. below, but in the following generation , the rice stem borer for instance, no oviposition or decreased laying is observed from the dosages at 3 Kr. to 1 Kr., and the hatching was possible from 1.5 Kr. below of irradiated larvae although laying and hatching are seemed in normal. In general, the lethal dose $50\%$ of tested infect materials at the larval stage can he classified some what 60-80 Kr. for Pine caterpillar, Fall webworm, Camphor silk moth and their relatives, at 40-60 Kr. for Gypsy moth, Monley prominent and some relatives and at 20-30 Kr. for House fly, Rice weevil, Pine sawfly etc. Plant parasitic nematodes such as Hirschmannia and Paratylenchus shown very high resistance to radiation and the LD-50 is observed from 100 Kr. or above. A concept to evaluate the radiosensitivity in insects by taxological family line as a practical measure is not answerable yet, but it ran he solved within the near future through the continuing experiments.

• Journal of Environmental Health Sciences
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• v.39 no.4
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• pp.369-375
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• 2013

Objectives: This study was conducted to identify factors determining the toxicity of manufactured silver nano-particles (AgNPs) on aquatic organisms. Methods: For this purpose, we prepared several AgNPs with varied characteristics, including hydrodynamic size (nano-$^{ABC}Ag^{Cit}\;vs$-sized-$^{ABC}Ag^{Cit}$), impurities ($^{ABC}Ag$ stock vs $^{ABC}Ag$), and citrate capping ($^{ABC}Ag^{Cit}$), using a commercially available manufactured AgNP ($^{ABC}Ag$ stock). Acute tests were conducted using larval zebrafish (Danio rerioI). In addition, in order to determine the ecotoxicological potentials of various capping agents, toxicity tests were conducted with microbes, waterfleas, and fish for eight different capping agents that are used for NPs. Results: The toxicity of AgNPs in terms of 96 h fish $LC_{50}$ increased in the following order: $^{ABC}Ag$ stock < $^{ABC}Ag=^{ABC}Ag^{Cit}=nano-^{ABC}Ag^{Cit}$ < ${\mu}$-sized-$^{ABC}Ag^{Cit}$ < $AgNO_3$. After removing impurities by dialysis, 96 h $LC_{50}$ value decreased significantly from $126.6{\mu}g/L$ (95% confidence intervals [CI]: 107.0-146.2) ($^{ABC}Ag$ stock) to $78.6{\mu}g/L$ (CI: 72.7-84.8) ($^{ABC}Ag$). For ${\mu}$-sized-$^{ABC}Ag^{Cit}$ (ranging between 3.9 and 40.6 nm) and $^{ABC}Ag^{Cit}$ (40.6 nm and $9.1{\mu}m$), the 96 h $LC_{50}$ of the former ($43.9{\mu}g/L$, CI: 36.0-51.7) was approximately two-fold lower than that of the latter ($87.0{\mu}g/L$, CI: 73.5-100.3). Conclusions: In this study, we found that for acute lethality, the contribution of impurities and particle size was significant, but that of citrate was negligible.

• Korean journal of applied entomology
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• v.53 no.4
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• pp.355-365
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• 2014

It has been unclear whether the diamondback moth, Plutella xylostella can overwinter in Korean field conditions. This study determined overwintering conditions of P. xylostella by conducting field exposure tests based on its cold tolerance and monitoring overwintering populations by direct examination of overwintering larval habitats and capturing adults with sex pheromone traps. In addition, the overwintering populations were analyzed using polymorphic genetic markers to trace their sources. When all immature stages of P. xylostella were exposed to $-5^{\circ}C$, which was the temperature much above their supercooling points, they significantly suffered with direct cold injuries, where larval stage was most tolerant to the cold injury. However, the exposure to $5^{\circ}C$ for a long period (4 weeks) did not give any significant cold injury to nonfeeding stages, while this treatment gave lethality to larval stage without diet. When all developmental stages of P. xylostella were exposed to open field conditions during winter, they exhibited significant decreases of survival rates. However, some protected and indoor conditions reduced the cold injuries and the diet provision significantly increased larval survival rates. Adult monitoring with sex pheromone during winter period indicated that the first captures were observed at similar periods at different locations (${\approx}260$ Km apart). The overwintering adults were captured until early April. Genetic variation of these overwintering populations was analyzed with polymorphic molecular markers, indicating significant genetic divergences among the overwintering populations. This study indicates that P. xylostella can overwinter in southern Korean fields or some protected greenhouses with host plants.