• Journal of Photoscience
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• v.9 no.2
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• pp.326-328
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• 2002

In many plant cells, the positions of chloroplasts change in response to changes in light conditions. In the epidermal cells of the aquatic angiosperm Vallisneria gigantea, the avoidance response of chloroplasts is induced specifically by irradiation with blue light of high intensity. Possible roles of actin cytoskeleton in the blue-light-induced avoidance response of chloroplasts were investigated by partial irradiation and phalloidin staining. We showed that the blue-light-dependent redistribution of chloroplasts was induced only in the limited area, where exposed to blue light, even in individual cells. In addition. in the exposed area, the configuration of actin filaments strikingly changed compared with that before the irradiation. Short and thick bundles of actin filaments surrounding the chloroplasts changed to much longer and thinner bundles with a more stretched array. In contrast, in the unexposed area, neither the distribution of chloroplasts nor the configuration of actin filaments exhibited any changes. Cytochalasin D and latrunculin B inhibited the avoidance response of chloroplasts concomitantly with the fragmentation of actin filaments. These results indicate that the reorganization of actin filaments plays a crucial role in the induction of avoidance response of chloroplasts.

• ALGAE
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• v.25 no.4
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• pp.197-204
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• 2010

Cytoskeletal changes were observed during cell division of the green alga Zygnema cruciatum using flourescein isothiocynate (FITC)-conjugated phallacidin for F-actin staining and FITC-anti-$\alpha$-tubulin for microtubule staining. Z. cruciatum was uninucleate with two star-shaped chloroplasts. Nuclear division and cell plate formation occurred prior to chloroplast division. Actin filaments appeared on the chromosome and nuclear surface during prophase, and the F-actin ring appeared as the cleavage furrow developed. FITC-phallacidin revealed that actin filaments were attached to the chromosomes during metaphase. The F-actin ring disappeared at late metaphase. At telophase, FITC-phallacidin staining of actin filaments disappeared. FITC-anti-$\alpha$-tubulin staining revealed that microtubules were arranged beneath the protoplasm during interphase and then localized on the nuclear region at prophase, and that the mitotic spindle was formed during metaphase. The microtubules appeared between dividing chloroplasts. The results indicate that a coordination of actin filaments and microtubules might be necessary for nuclear division and chromosome movement in Z. cruciatum.

• Journal of Periodontal and Implant Science
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• v.26 no.4
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• pp.1003-1012
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• 1996

The induction of a phenotype with preoperties may have clinical significance in the acceleration of the wound-healing process. Wound contraction involves a specialized cell known as the myofibroblast. The myofibroblasts can be identified by their intense staining of actin bundles with anti-actin antibody. Tissue-specific actin distribution is correlated with the contractile activity of the myofibroblasts and smooth muscle etc. This study was performed to determine the expression of actin filaments in the cytoplasm of cultured human gingival fibroblsts after GaAs laser(BIOSAER, Korea) irradiation. Human gingival fibroblasts were cultured from explants of normal interdental gingival tissue. The third-generation fibroblasts were used for immunohistochemical study. The cultured fibroblasts were exposed $0.53joule/cm^2$(lmW, 7 mimutes) of energy density, and then observed by immunohistochemical method using, rabbit anti0gelsolin, hen smooth muscle polyclonal antibody(Chemicon international inc.), and biotinylated goat anti-rabbit IgG(Vectastain) 24-, 36-, 48-hour after laser irradiation Following results were obtained ; 1. In nonirradiated cultures, round shaped active fibroblasts with abundant cytoplasm and prominet nucleoli were observed. 2. In 24- and 36-hour cultures after laser irradiation, spindle shaped cells with long process were observed. The intensity of stain was seen in cytoplasm of these modified fibroblasts. 3. In 48-hoour cultures after laser irradiation, stained spindle shape cell were not observed. The results suggest that the effect of the galium-arsenide laser treatment on cultured gingival fibroblasts is the rapid development of cytoplasmic actin filaments.

• Proceedings of the Korean Biophysical Society Conference
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• 2003.06a
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• pp.24-24
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• 2003

Actin filament is a major cytoskeleton in synapses and highly enriched in the presynaptic and postsynaptic compartments. Their roles in synaptic vesicle recycling and synaptogenesis have been extensively studied but functional evidence whether actin filaments are involved in these processes is as yet lacking. Dysfunction in synaptic vesicle recycling causes various diseases such as Alzheimer's disease, Schizophrenia, Bipolar disease, depression etc.

• Journal of the Korean Applied Science and Technology
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• v.24 no.1
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• pp.61-66
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• 2007

X-ray diffraction studies have been made to investigate the effects of binding of ADP, ADP+Vi, ADP+AIF4, $ADP+BeF_3$ on the structure of glycerinated rabbit skeletal muscle in the rigor state. Although these phosphate analogs are known to bind actively cycling myosin heads, it is not clear whether they can bind to the attached heads in the rigor muscle. We have found that these analogs can bind to the myosin heads attached to actin filaments in the rigor state. The present results indicate that (1) bound myosin heads altered their conformation in the proximal end toward the plane perpendicular to the fiber axis when MgADP bound to them, and (2) myosin heads were dissociated substantially (up to 50%) from actin filaments but still remained in the vicinity of actin filaments when MgADP and metallofluorides (AIF4 and BeF3) or vanadate bound to them. We detected new conformations of myosin heads attached to actin filaments when they had MgADP or ADP.Pi analogs. We report here these findings on the effects of MgADP and MgADP+phosphate analogs to the rigor crossbridges.

• Proceedings of the Korean Biophysical Society Conference
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• 2003.06a
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• pp.67-67
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• 2003

Filamentous actin (F-actin) is a two stranded long helix that performs structural function in eukaryotic cells. F-actin had been assembled from Alexa-labeled G-actin and had been confined in microchannel. The fluctuation of single filaments was observed by fluorescence optical microscopy. We measured Tangent-tangent Correlation Function G(s) (where s is the distance along the contour of the chain), which tells us the confining wall effect of wormlike semi-flexible polymers as well as the flexural rigidity, such as persistence length.

• Applied Microscopy
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• v.29 no.4
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• pp.437-450
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• 1999

Bile canaliculi are the structure delivering bile secreted by hepatocytes into the bile passage. Bile secretion is mainly controlled by the cytoskeletal elements, mainly of actin in the microvilli, pericanalicular web. Most studies on the bile secretion have been done in viva situation, however, to control the various parameters in vitro culture system seem to be more useful. To set up an in vitro experimental system, the investigator isolated hepatocytes with an enzymatic method using a mixture of collagenase and hyaluronidase from normal Sprague-Dawley rat liver and cultured. Isolated hepatocytes were round and formed cords in culture. Microvilli covered the whole surface of hepatocytes. Bile canaliculi were formed between hepatocytes and were characterized by the presence of microvilli of various lengths and shapes mainly arising from small surface mounds. Actin filament core in the microvilli and pericanalicular actin web were incomplete. After cytochalasin D treatment, cultured hepatocytes were round but the surface were irregular with surfacen blebs, folds and grooves. Microvilli on the surface were scarce. Bile canaliculi were markedly dilated often with the detached junctional complexes. Bile canaliculi lacks microvilli almost completely and extended into the pericanalirular cytoplasm showing complex vacuolar and tubular structures by transmission electron mciroscopy. Pericanalicular actin web, intermediate filaments were hardly identified. Subsurface actin filaments were scattered scarcely under the cell membranes. These results suggest that hepatocytes isolated from rats can survive and form bile canaliculi in culture and the actin filaments are involved in the formation and/or maintenance of the bile canaliculi.

• Parasites, Hosts and Diseases
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• v.44 no.4 s.140
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• pp.331-341
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• 2006

Actin binding proteins play key roles in cell structure and movement particularly as regulators of the assembly, stability and localization of actin filaments in the cytoplasm. In the present study, a cDNA clone encoding an actin bundling protein named as AhABP was isolated from Acanthamoeba healyi, a causative agent of granulomatous amebic encephalitis. This clone exhibited high similarity with genes of Physarum polycephalum and Dictyostelium discoideum, which encode actin bundling proteins. Domain search analysis revealed the presence of essential conserved regions, i.e., an active actin binding site and 2 putative calcium binding EF-hands. Transfected amoeba cells demonstrated that AhABP is primarily localized in phagocytic cups, peripheral edges, pseudopods, and in cortical cytoplasm where actins are most abundant. Moreover, AhABP after the deletion of essential regions formed ellipsoidal inclusions within transfected cells. High-speed co-sedimentation assays revealed that AhABP directly interacted with actin in the presence of up to $10{\mu}M$ of calcium. Under the electron microscope, thick parallel bundles were formed by full length AhABP, in contrast to the thin actin bundles formed by constructs with deletion sites. In the light of these results, we conclude that AhABP is a novel actin bundling protein that is importantly associated with actin filaments in the cytoplasm.

• Proceedings of the Botanical Society of Korea Conference
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• 2001.04a
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• pp.25-25
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• 2001

• Biomedical Science Letters
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• v.26 no.1
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• pp.1-7
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• 2020

Alzheimer's disease (AD) is the most common neurodegenerative disorder and is expected to become more and more widespread as life expectancy increases. New therapeutic target, as well as the identification of mechanisms responsible for pathology, is urgently needed. Recently, microglial actin cytoskeleton has been proposed as a beneficial role in axon regeneration of brain injury. This review highlights in understanding of the characteristics of microglial actin cytoskeleton and discuss the role of specific actin-interacting proteins and receptors in AD. The precise mechanisms and functional aspects of motility by microglia require further study, and the regulation of microglial actin cytoskeleton might be a potential therapeutic strategy for neurological diseases.