• Molecules and Cells
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• v.27 no.1
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• pp.1-3
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• 2009

Mitotic spindle mediates the segregation of chromosomes in the cell cycle and the proper function of the spindle is crucial to the high fidelity of chromosome segregation and to the stability of the genome. Nucleation of microtubules (MTs) from centrosomes and chromatin represents two well-characterized pathways essential for the assembly of a dynamic spindle in mitosis. Recently, we identified a third MT nucleation pathway, in which existing MTs in the spindle act as a template to promote the nucleation and polymerization of MTs, thereby efficiently amplifying MTs in the spindle. We will review here our current understanding on the molecular mechanism, the physiological function and the cell-cycle regulation of MT amplification.

• Proceedings of the KSAR Conference
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• 2002.06a
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• pp.51-51
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• 2002

Despite of importance of integrated events of nucleus and microtubule remodeling in nuclear transferred embryos with somatic cells, little information is available on this subject. In this study we compared chromatin, r-tubulin and microtubule organization in porcine oocytes following somatic cell nuclear transfer and parthenogenetically activation in order to clarify nuclear remodeling process and to demonstrate centrosome inheritance during nuclear transfer. (omitted)

• Journal of Plant Biology
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• v.32 no.3
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• pp.151-162
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• 1989

Secretory ducts in the stem of Panax ginseng seedlings are observed with light and electron microscopes to clarify development of the epithelial cells of secretory ducts. Secretory duct initial cell is developed from procambial cell which originated from initial cell is differentiated into ipithelial cell ofsecretory ducts. Intercellular space between the epithelial cells are gradually expanded and differentiated into duct lumen. Disintegrations of epithelial cells occur throughout all the stages of development. The cytoplasm of epithelial cells darken and the epithelial cell wall are lysed, preceding their disintegraton. In the epithelial cell organelles are scattered in the cytoplasm. Development of vcuoles are sparse at the early stage. Starch grains decreased gradually, while lipid droplets increased. Free ribosomes are distributed throughout the cytoplasm and secretory vesicles which originated from rough endoplasmic reticulum and Golgi complex are fused with the plasmalemma. These suggest that the cellular metabolism is active. Microtubules and plasmodesmata are typically observed in the thickened epithelial cell wall. Secretions are accumulated in duct lumen.

• Molecules and Cells
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• v.41 no.1
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• pp.45-49
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• 2018

Autophagy is a lysosome-dependent degradation process that is essential for maintaining cellular homeostasis. In recent years, more studies have focused on the late stages of autophagy. Our group discovered and studied the terminal step of autophagy, namely autophagic lysosome reformation (ALR). ALR is the process that regenerates functional lysosomes from autolysosomes, thus maintaining lysosome homeostasis. ALR involves clathrin-mediated membrane budding from autolysosomes, elongation of membrane tubules along microtubules with the pulling force provided by the motor protein KIF5B, proto-lysosome scission by dynamin 2, and finally maturation of proto-lysosomes to functional lysosomes. In this review, we will summarize progress in unveiling the molecular mechanisms underlying ALR and its potential pathophysiological roles.

• Fisheries and Aquatic Sciences
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• v.10 no.4
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• pp.196-199
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• 2007

The spermatozoa of Leiocassis nitidus are relatively simple cells composed of a spherical head, a short midpiece, and a tail, as in most Siluriformes. The ultrastructure is characterized by the following features: Acrosome absent, as in most teleosts; around nucleus about $1.8\;{\mu}m$ long, with a deep nuclear fossa containing the proximal and distal centrioles and mitochondria. Two centrioles approximately $180^{\circ}$ from each other; 10 or more mitochondria surrounding the axoneme (with a 9+2 microtubular pattern), arranged in two layers in the postnuclear cytoplasm and separated from the axoneme by the cytoplasmic canal. Two lateral fins on the same plane as the two central microtubules; doublets 3 and 8, which are ultrastructural characteristics of the sperma tail unlike other siluroids laking the lateral fins.

• Fisheries and Aquatic Sciences
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• v.3 no.3_4
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• pp.205-212
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• 2000

Light and electron microscopical characteristics of Perkinsus sp. parasitizing in Manila clam, Ruditapes philippinarum, in Korea were investigated. Trophozoite within the tissue was spherical or ovoid and ranged $2.5-10.5\mu m$ $(mean = 6.2\mu m)$ in diameter. Trophozoite had a nucleus with a prominent nucleolus and a large cytoplasmic vacuole within the cytoplasm. Single trophozoite was phagocytozed by host hemocyte and cluster cells were encapusulated by hemocytes aggregation within the host tissues. Hypnospores incubated in thioglycollate medium (FTM) for 1 to 15 days were also spherical or ovoid and ranged $10-132\mu m$ $(mean\pm S.D.\;:\;44.25\pm 7.91\mu m)$ in diameter. Zoospores were spherical or ovoid, had a nucleus and two flagella. Zoospores contained apical complex, which consisted of conoid, subpellicular microtubules, rhoptries and rectilinear micronemes.

• BMB Reports
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• v.43 no.12
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• pp.795-800
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• 2010

Huntingtin-interacting protein 1-related (HIP1r) is known to function in clathrin-mediated endocytosis and regulation of the actin cytoskeleton, which occurs continuously in non-dividing cells. This study reports a new function for HIP1r in mitosis. Green fluorescent protein-fused HIP1r localizes to the mitotic spindles. Depletion of HIP1r by RNA interference induces misalignment of chromosomes and prolonged mitosis, which is associated with decreased proliferation of HIP1r-deficeint cells. Chromosome misalignment leads to missegregation and ultimately production of multinucleated cells. Depletion of HIP1r causes persistent activation of the spindle checkpoint in misaligned chromosomes. These findings suggest that HIP1r plays an important role in regulating the attachment of spindle microtubules to chromosomes during mitosis, an event that is required for accurate congression and segregation of chromosomes. This finding may provide new insights that improve the understanding of various human diseases involving HIP1r as well as its fusion genes.

• Applied Microscopy
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• v.27 no.3
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• pp.309-320
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• 1997

The spermatogenesis of korean leech, Whitmania edentula was observed, using both light and electron microscopes. The spermatogonium and maturing spermatozoon are connected with long cytoplasmic process to the cytophore, which supplys nutrition to the germ cells and supports synchronous maturity. The truck of korean leech is divided into three regions; a long ladder-shaped acrosome and head, long middle piece and long tail. Long head region twists to the dextral helix, and nuclei are surrounded with microtubules (manchette).The nebenkern formed with long mitochondrion exists in the middle pieces, and a long tail of Whitmania edentula ($9\times2+1$ axoneme) differs from the $9\times2+2$ axoneme of Rhynchobdellae. The late cytophore is mostly formed with crystalloid matter and a number of lysosomes, and matured spermatozooms are engulfed into the late cytophore.

• Molecules and Cells
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• v.20 no.2
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• pp.256-262
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• 2005

The neuronal cytoskeleton is essential for establishment of neuronal polarity, but mechanisms controlling generation of polarity in the cytoskeleton are poorly understood. The nonreceptor tyrosine kinase, Fer, has been shown to bind to microtubules and to interact with several actin-regulatory proteins. Furthermore, Fer binds p120 catenin and has been shown to regulate cadherin function by modulating cadherin-${\beta}$-catenin interaction. Here we show involvement of Fer in neuronal polarization and neurite development. Fer is concentrated in growth cones together with cadherin, ${\beta}$-catenin, and cortactin in stage 2 hippocampal neurons. Inhibition of Fer-p120 catenin interaction with a cell-permeable inhibitory peptide (FerP) increases neurite branching. In addition, the peptide significantly delays conversion of one of several dendrites into an axon in early stage hippocampal neurons. FerP-treated growth cones also exhibit modified localization of the microtubule and actin cytoskeleton. Together, this indicates that the Fer-p120 interaction is required for normal neuronal polarization and neurite development.

• Proceedings of the Korean Biophysical Society Conference
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• 2001.06a
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• pp.34-34
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• 2001

Survivin, an apoptosis inhibitor/cell-cycle regulator, is critically required for suppression of apoptosis and ensuring normal cell division in the G2/M phase of the cell cycle. It is highly expressed in a cell cycle-regulated manner and localizes together with caspase-3 on microtubules within centrosomes. Whether survivin is a physiologically relevant caspase inhibitor has been unclear due to the difficulties with obtaining correctly folded survivin and finding right conditions for inhibition assay.(omitted)