• Molecules and Cells
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• v.44 no.8
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• pp.602-612
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• 2021

DNA methylation is an important epigenetic mechanism affecting genome structure, gene regulation, and the silencing of transposable elements. Cell- and tissue-specific methylation patterns are critical for differentiation and development in eukaryotes. Dynamic spatiotemporal methylation data in these cells or tissues is, therefore, of great interest. However, the construction of bisulfite sequencing libraries can be challenging if the starting material is limited or the genome size is small, such as in Arabidopsis. Here, we describe detailed methods for the purification of Arabidopsis embryos at all stages, and the construction of comprehensive bisulfite libraries from small quantities of input. We constructed bisulfite libraries by releasing embryos from intact seeds, using a different approach for each developmental stage, and manually picking single-embryo with microcapillaries. From these libraries, reliable Arabidopsis methylome data were collected allowing, on average, 11-fold coverage of the genome using as few as five globular, heart, and torpedo embryos as raw input material without the need for DNA purification step. On the other hand, purified DNA from as few as eight bending torpedo embryos or a single mature embryo is sufficient for library construction when RNase A is treated before DNA extraction. This method can be broadly applied to cells from different tissues or cells from other model organisms. Methylome construction can be achieved using a minimal amount of input material using our method; thereby, it has the potential to increase our understanding of dynamic spatiotemporal methylation patterns in model organisms.

• Molecules and Cells
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• v.42 no.5
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• pp.379-385
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• 2019

Non-coding RNAs (ncRNAs) comprise various RNA species, including small ncRNAs and long ncRNAs (lncRNAs). ncRNAs regulate various cellular processes, including transcription and translation of target messenger RNAs. Recent studies also indicate that ncRNAs affect organismal aging and conversely aging influences ncRNA levels. In this review, we discuss our current understanding of the roles of ncRNAs in aging and longevity, focusing on recent advances using the roundworm Caenorhabditis elegans. Expression of various ncRNAs, including microRNA (miRNA), tRNA-derived small RNA (tsRNA), ribosomal RNA (rRNA), PIWI-interacting RNA (piRNA), circular RNA (circRNA), and lncRNA, is altered during aging in C. elegans. Genetic modulation of specific ncRNAs affects longevity and aging rates by modulating established aging-regulating protein factors. Because many aging-regulating mechanisms in C. elegans are evolutionarily conserved, these studies will provide key information regarding how ncRNAs modulate aging and lifespan in complex organisms, including mammals.

• BMB Reports
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• v.56 no.2
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• pp.49-55
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• 2023

Aging is characterized by a gradual decline in biological functions, leading to the increased probability of diseases and deaths in organisms. Previous studies have identified biological factors that modulate aging and lifespan, including non-coding RNAs (ncRNAs). Here, we review the relationship between aging and tRNA-derived small RNAs (tsRNAs), ncRNAs that are generated from the cleavage of tRNAs. We describe age-dependent changes in tsRNA levels and their functions in age-related diseases, such as cancer and neurodegenerative diseases. We also discuss the association of tsRNAs with aging-regulating processes, including mitochondrial respiration and reduced mRNA translation. We cover recent findings regarding the potential roles of tsRNAs in cellular senescence, a major cause of organismal aging. Overall, our review will provide useful information for understanding the roles of tsRNAs in aging and age-associated diseases.

• Korean Journal of Ichthyology
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• v.35 no.1
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• pp.30-38
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• 2023

The feeding ecology of the eight barbel loach, Lefua costata, were investigated in the Jusucheon (Stream), Namyang-ri, Okgye-myeon, Gangneung-si, Gangwon-do, Korea from January to December 2013. L. costata mainly fed from March to December when the water temperature was higher than 5℃, and the feeding rate peaked in April~May and September~October. Their main food organisms analyzed by the index of relative importance (IRI) were Diptera (77.1%), Ephemeroptera (20.3%), Trichoptera (1.7%) and Odonata (0.4%) in Insecta. Other food organisms were various, such as Arhynchobdellida (0.6%) and Tubificida (0.1%) of Annelida, Nematoda (0.2%), fish (Actinopterygii, 0.1%), and Veneroida (0.01%) of the Mollusca. Major seasonal food organisms were Diptera (55.4%) and Ephemeroptera (41.6%) in spring, Diptera (92.7%) and Anelida (6.8%) in summer, Diptera (70.8%), Ephemeroptera (9.0%), Trichoptera (8.1%) and Annelida (7.7%) in autumn. By age, juvenile (0+) tended to eat only Diptera (mainly Chironomidae, 98.2%) that were relatively small in prey size. However, as it grew, the proportion of Diptera gradually decreased, and the proportion of relatively large Mayflies and Annelids increased. The size of the prey organisms showed rapid growth, with 2.5±1.05 mm for juvenile (0+), 3.2±1.29 mm for one year (1+), 3.7±2.05 mm for two years (2+), and 6.8±4.97 mm for three years or more (≥3+).

• Applied Microscopy
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• v.10 no.1_2
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• pp.27-32
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• 1980

A case of cutaneous leishmaniasis developed in a 48 year old Korean male who returned from middle east was studied by light and electron microscopic observations. Light microscopically, the lesion consisted of heavy chronic ill-defined granulomatous inflammation involving entire thickness of the dermis, composed of mainly histiocytic and small mononuclear cell infiltrations without evidence of necrosis or giant cell formation. Giemsa staining revealed numerous intracellular micro-organisms within histiocytes, showing dark stained central dot surrounded by light stained cytoplasm. Electron microscopically, the organisms were observed mostly ovoid in shape and frequently binary mitotic features within the host cells. follicle consisted of double unit membranes and microtubules, which are immediately below these membrnae. A long kinetoplast was noted within a very elongated mitochondrion at the center of the organisms and a flagella rose in front of the kineoplast but ended within the cytoplasm. Large numbers of free ribosomes, occasional Golgi complex and SER were also noted, but RER was seldom found. These ultrastructural features corresponded to promastigote stage of Leishmania tropica. In principle, leishmaniasis is a tropical disease and can not be found in temperate zone. However, travel to mideast by many Koreans may contract this disease while they are in endemic regions.

• Korean Journal of Environmental Biology
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• v.40 no.4
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• pp.374-386
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• 2022

Phytoplankton communities, with emphasis on picoplankton and nanoplankton, were investigated in Gamak Bay, South Korea, where freshwater input and coastal water intrusion shape ecosystem functions. Shellfish farms and fish farms are located in the inner bay and outer bay, respectively, and tides translocate uneaten food and urine production from aquaculture farms toward the inner bay. Water masses were distinctly different based on a significantly different density between the surface and bottom layer and among three water masses, including the inner bay, outer bay, and Yeosu Harbor. Phytoplankton communities were quantified using flow cytometry and size-fractionated chlorophyll-a (chl-a) was measured. Salinity was a principal variable separating phytoplankton communities between the surface and bottom layer, whereas Si(OH)₄ controlled the communities in the inner bay, and NH₄⁺ and PO₄^3- governed the outer bay communities. While phycocyanin-containing (PC) cyanobacteria dominated in the outer bay, phycoerythrin-containing (PE) cyanobacteria dominance occurred with cryptophyte dominance, indicating that nutrients affected the distribution of pico- and nanoplankton and that cryptophytes potentially relied on a mixotrophic mode by feeding on PE cyanobacteria. Interestingly, picoeukaryotes and eukaryotes larger than 10 ㎛ were mostly responsible for the ecological niche in the western region of the bay. Given that chl-a levels have historically declined, our study highlights the potential importance of increased small phytoplankton in Gamak Bay. Particularly, we urge an examination of the ecological role of small phytoplankton in the food supply of cultivated marine organisms.

• Korean Journal of Ichthyology
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• v.9 no.2
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• pp.221-227
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• 1997

Feeding habits of Leiognathus nuchalis collected from the eelgrass bed in Kwangyang Bay from January 1994 to December 1994 were studied. Leiognathus nuchalis was a carnivore which mainly consumed copepods and crab larvae. Its diets included small quantities of polychaetes, amphipods, mysids, caridean shrimps. It showed ontogenetic changes in feeding habits. In an initial feeding stage, copepods were major food organisms. However, crab larvae and polychaetes were heavily selected with increasing fish size. Although copepods and crab larvae were major prey organisms for all seasons, the relative proportion of these two food items changed with season.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2010.10a
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• pp.730-733
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• 2010

The Green Lamp Fixture (GLF) of LED prepared with thin panel structure was investigated for illumination of street lamps and other lighting system uses, which was also very useful to aquaculture and aquafarm lighting uses, or fish luring lights and marine aquanautics of aquamarinautics (aquamarine+aquanautics) uses, etc. In the case of fish luring lights, it was verified that the fish luring of Green Lamp Fixture of LED was very effective for phototaxis movement and ecological community promotion to the micro-living things of organisms and the small fries and fishes, like as 'crowding together'. For the aquaculture lightings, it was also very excellent in waterproof and heat-sink properties, photosynthetic growing of algae and micro-organisms, water-weeds and seaweeds living underwater.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.51 no.3
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• pp.305-312
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• 2018

This study was carried out to investigate euphausiid abundance in an acoustic survey from March 2010 to July 2010 to suggest reasonable usage and management of the euphausiid Euphausia pacifica in the coastal area of Guryongpo Pohang. The acoustic data were analyzed by the 2-frequency difference method and the distorted wave born approximation acoustical theoretical model, which is used for organisms of weak target strength with small scatter, such as euphausiid scatter, among other marine organisms. The distribution and monthly density of euphausiids were estimated in the survey area. The results show that the volume back scattering strength frequency difference for euphausiid was 13.91-7.6 dB, and their monthly averag density was $28.2g/m^2$.

• Fisheries and Aquatic Sciences
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• v.8 no.4
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• pp.201-206
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• 2005

Microalgae are widely used for mass culture of the rotifer Brachionus plicatilis in aquaculture. Since the nutritional value of the rotifer is closely related to its food, the nutritional value of its food should be known in detail. Chlorella ellipsoidea and Nannochloris oculata are re­presentative food organisms for rotifers that are easily cultured. Therefore, the nutritional values of these micro algae were examined for ultrasmall, small, and large rotifers and Artemia nauplii. Chlorella ellipsoidea contained seven times more total fatty acids than N. oculata. The three types of rotifer fed N. oculata contained more amino acids than those fed C. ellipsoidea. However, the total fatty acids of the rotifers fed each microalga species differed according to the type of rotifer. Newly hatched Artemia nauplii contained more protein and had a higher dry weight than those fed microalgae for 6 h. As with the rotifers, the Artemia nauplii fed N. oculata contained more protein and amino acids than those fed C. ellipsoidea, while the reverse was true for the total fatty acid content. Our results suggest that N. oculata is a good supply of protein, while C. ellipsoidea is a good source of lipids as food organisms for rotifers and Artemia nauplii in aquaculture.