• Proceedings of the Botanical Society of Korea Conference
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• 1999.07a
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• pp.85-89
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• 1999

Somatic embryogendesis is one of good examples of the basic research for plant embryo development as well as an important technique for plant biotechnology. This paper describes the direct somatic embryogenesis from zygotic embryos of Panax ginseng is reversely related to normal axis growth of zygotic embryos by the experiment of various chemical treatments. Under the normal growth condition, the apical tips of embryo axis produced an agar-diffusible substance, which suppressed somatic embryo development from cotyledons. Although the cells of zygotic embryos were released from the restraint of embryo axis, various factors were still involved for somatic embryo development. Electron microscopic observation revealed that the ultrastructure of cells of cotyledon epidermis markedly changed before initiation of embryonic cell division, probably indicating reprogramming events into the cells embryogenically determined state. Polar accumulation of endogenous auxin or cell-cell isolation by plasmolysis pre-treatment is the strong inducer for the somatic embryo development. The cells for the process of somatic embryogenesis might be determined by the physiological conditions fo explants and medium compositions. Direct somatic embryos from cotyledons fo ginseng were originated eithrer from single or multiple cells. The different cellular origin of somatic embryos was originated either from single or multiple cell. The different cellular origin of somatic embryos was depended on various developmental stages of cotyledons. Immature meristematic cotyledons produced multiple cell-derived somatic embryos, which developed into multiple embryos. While fully mature cotyledons produced single cell-derived single embryos with independent state. Plasmolysis pretreatment of cotyledons strongly enhanced single cell-derived somatic embryogenesis. Single embryos were converted into normal plantlets with shoot and roots, while multiple embryos were converted into only multiple shoots. GA3 or a chilling treatment was prerequisite for germination and plant conversion. Low concentration of ammonium ion in medium was necessary for balanced growth of root and shoot of plantlets. Therefore, using above procedures, successful plant regeneration of ginseng was accomplished through direct single embryogenesis, which makes it possible to produce genetically transformed ginseng efficently.

• Clinical and Experimental Reproductive Medicine
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• v.37 no.1
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• pp.13-23
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• 2010

Objective: The present study was carried out to induce differentiation of human embryonic stem cells (hESCs) into germ cells and to establish a culture condition for single hESCs dissociated by enzyme. Methods: Embryonic body (EB) was formed by hanging drop culture for 3 days from hESCs colony. The EBs were cultured in the medium supplemented with retionic acid (RA) or/and bone morphogenetic protein-4 (BMP4) for 14 days to differentiate into germ cells. Germ cell specific markers, c-kit and VASA were used for immunohistochemistry of EB. Human ESCs colonies were dissociated into single cells by Collagenase, Tryple and Accutase, and then colony formation rate of the single cells was examined. Rho-associated kinase inhibitor (ROCK inhibitor, Y27632) was added into the culture medium of single cells to reduce the apoptotic damage during the dissociation. Results: Single cells dissociated with Tryple or Accutase showed higher colony formation rates compared to the cells dissociated with Collagenase. Seeding of $5{\times}10^3$ cells/well (4 well dish) was efficient to obtain high colony formation rate compared to other concentrations of seeding cell. Addition of Y27632 significantly increased the colony formation rate of the single cells dissociated by Tryple. Immunohistochemistry of EB with c-kit and VASA markers showed a weak fluorescence signals compared to the signals from the testicular tissue. Conclusion: Dissociation with Tryple was useful to obtain healthy single cells and addition of Y27632 was beneficial for survival and colony formation of the single cells. Unlike other studies, we just observed a dim fluorescence staining of the germ cell markers, probably caused by the short-term culture for the differentiation of EB compared to other studies.

• The Korean Journal of Physiology
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• v.28 no.2
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• pp.151-157
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• 1994

Intracellular free $Ca^{2+}$ contributes to regulation of various events occurring in vascular smooth muscle cells. One of these events is modulating the membrane iou currents. Single smooth muscle cells were isolated from rabbit mesenteric artery. Three kinds of $Ca^{2+}-activated\;current$ were studied with the patch clamp method. $Ca^{2+}-activated\;K^+\;current$ with a large oscillation was recorded in the depolarized potential range. The single channel conductance of this current was about 250 pS. It was abolished by replacing intracellular $K^+\;with\;Cs^+$. A $Ca^{2+}-activated$ nonselective cation current was observed in both the depolarized and hyperpolarized potential ranges. And it was blocked by replacement of extracellular $Na^+$ with N-methylglucamine (NMG) or extracellular application of $Cd^{2+}$. $Ca^{2+}-activated\;Cl^-\;current$ was revealed in the whole voltage range and was blocked by niflumic acid. These results indicate that at least three kinds of $Ca^{2+}-activated$ ionic currents exist in smooth muscle cells from rabbit superior mesenteric artery.

• Journal of the Korean Ceramic Society
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• v.43 no.12 s.295
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• pp.775-780
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• 2006

Mechanical and electrical performance of anode-supported SOFC single cells were analyzed after thermal cyclic operation. The experiments of thermal cyclic cell-operation were carried out four times and performance of each cell was measured at different temperatures of 650, 700, and $750^{\circ}C$, respectively. As increasing the number of thermal cycle test, single cells showed poor I-V characteristics and lower 4-point bending strength. The anode polarization was also measured by AC-impedance analysis. The observation of the microstructure of the anodes in single cells proved that the average particle size of Ni decreased and the porosity of anode increased. It is thought that the thermal cycle caused the degradation of performance of single cells by reducing the density of three-phase boundary region.

• Animal cells and systems
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• v.15 no.3
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• pp.251-258
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• 2011

Ciliates are considered one of the most diverse protozoa and play significant roles in ecology. For successful taxonomic study of these microscopic eukaryotes, a staining procedure is necessary, due mainly to intrinsic difficulties in recognizing characteristics from living cells. Although molecular taxonomy has been used to resolve the ambiguities associated with traditional morphology-based taxonomy, extraction of genomic DNA from stained ciliate cells is not available yet. In the present study, we describe a method to extract genomic DNA from a single protargol-impregnated euplotid cell. By using $HgCl_2$ as a fixative and modulating the exposure time of bleach solution in the protargol impregnation, high-quality genomic DNA can successfully be extracted from a stained single cell with minimal loss of morphological integrity. This technique will contribute to the effectiveness of combined approaches of molecular and morphological taxonomy from single ciliate cells.

• Mass Spectrometry Letters
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• v.14 no.4
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• pp.121-140
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• 2023

It is becoming more and more clear that each cell, even those of the same type, has a unique identity. This sophistication and the diversity of cell types in tissue are what are pushing the necessity for spatially distributed omics at the single-cell (SC) level. Single-cell chemical assessment, which also provides considerable insight into biological, clinical, pharmacodynamic, pathological, and toxicity studies, is crucial to the investigation of cellular omics (genomics, metabolomics, etc.). Mass spectrometry (MS) as a tool to image and profile single cells and subcellular organelles facilitates novel technical expertise for biochemical and biomedical research, such as assessing the intracellular distribution of drugs and the biochemical diversity of cellular populations. It has been illustrated that ambient mass spectrometry (AMS) is a valuable tool for the rapid, straightforward, and simple analysis of cellular and sub-cellular constituents and metabolites in their native state. This short review examines the advances in ambient mass spectrometry (AMS) and ambient mass spectrometry imaging (AMSI) on single-cell analysis that have been authored in recent years. The discussion also touches on typical single-cell AMS assessments and implementations.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.18 no.1
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• pp.31-45
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• 1988

The author studied the histopathologic changes according to a single or a split dose and the time after irradiation on the acinar cells of rat parotid gland. 99 Sprague Dawley rats, weighing about l20gm, were divided into control and 3 experimental groups. In experimental groups, GroupⅠ and Ⅱ were delivered a single dose of l5Gy, 18Gy and Group Ⅲ and Ⅳ were delivered two equal split doses of 9Gy, 10.5Gy for a 4 hours interval, respectively. The experimental groups were delivered by a cobalt-60 teletherapy unit with a dose rate of 222cGy/min, source-skin distance of 50㎝, depth of l㎝ and a field size of l2×5㎝. The animals were sacrificed at 1, 2, 3, 6, 12 hours, 1, 3, 7 days after irradiation and examined by light and electron microscopy. The results were as follows: 1. As the radiation dose increased and the acinar cells delivered a single dose exposure were more damaged, and the change of acinar cells appeared faster than those of a split dose exposure. 2. The histopathologic change of acinar cells appeared at 1 hour after irradiation. The recovery from damaged acinar cells appeared at 1 day after irradiation and there was a tendency that the recovery from damage of a split dose exposure was somewhat later than that of a single dose exposure. 3. Light microscope showed atrophic change of acinar cells and nucleus, degeneration and vesicle formation of cytoplasm, widening of intercellular space and interlobular space. 4. Electron microscope showed loss of nuclear membrane, degeneration of nucleus and nucleoli, clumping of cytoplasm, widening and degeneration of rough endoplasmic reticulum, loss of cristae of mitochondria, lysosome, autophagosome and lipid droplet. 5. Electron microscopically, the change of rough endoplasmic reticulum was the most prominent and this appeared at 1 hour after irradiation as early changes of acinar cells. The nuclear change appeared at 2 hours after irradiation and the loss of cristae of mitochondria was observed at 2 hours after irradiation in all experimental groups.

• BMB Reports
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• v.54 no.10
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• pp.505-515
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• 2021

Human pluripotent stem cells (hPSCs) include human embryonic stem cells (hESCs) derived from blastocysts and human induced pluripotent stem cells (hiPSCs) generated from somatic cell reprogramming. Due to their self-renewal ability and pluripotent differentiation potential, hPSCs serve as an excellent experimental platform for human development, disease modeling, drug screening, and cell therapy. Traditionally, hPSCs were considered to form a homogenous population. However, recent advances in single cell technologies revealed a high degree of variability between individual cells within a hPSC population. Different types of heterogeneity can arise by genetic and epigenetic abnormalities associated with long-term in vitro culture and somatic cell reprogramming. These variations initially appear in a rare population of cells. However, some cancer-related variations can confer growth advantages to the affected cells and alter cellular phenotypes, which raises significant concerns in hPSC applications. In contrast, other types of heterogeneity are related to intrinsic features of hPSCs such as asynchronous cell cycle and spatial asymmetry in cell adhesion. A growing body of evidence suggests that hPSCs exploit the intrinsic heterogeneity to produce multiple lineages during differentiation. This idea offers a new concept of pluripotency with single cell heterogeneity as an integral element. Collectively, single cell heterogeneity is Janus-faced in hPSC function and application. Harmful heterogeneity has to be minimized by improving culture conditions and screening methods. However, other heterogeneity that is integral for pluripotency can be utilized to control hPSC proliferation and differentiation.

• Journal of the Korean Society for Precision Engineering
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• v.27 no.5
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• pp.85-91
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• 2010

In this paper, we present details on fabrication of single-cell electroporation microdevice, practical experiments of single-cell electroporation with our fabricated microdevice. Also, the continuous electroporation for the continuous flow of cells is used for high-throughput electroporation. The delivery efficiency and cell viability tests are provided and the successful GFP transfection into cells is also evaluated with a fluorescent microscope after electroporation. This device enables to reduce the size of samples and thus the use of small amount of reagents. Also, it makes it possible to permit to avoid cell discrimination (transfected cells versus non-transfected cells) encountered when traditional bulk electroporation is held.

• Proceedings of the Korean Biophysical Society Conference
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• 2003.06a
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• pp.56-56
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• 2003

Isolated single pancreatic acinar cells have long been used as a good model for studying many kinds of signaling processes due to their good structural and functional polarities without a significant validation. In this study, we have examined morphological and functional changes of the dissociated single pancreatic acinar cells by imaging cytosolic Ca$\^$2+/ concentration, exocytosis of granules, and by observing their shapes with confocal microscopy.