• Applied Microscopy
• /
• v.22 no.2
• /
• pp.75-83
• /
• 1992

Comparative study on the spermatogenesis of two kinds of Korean planarias, Dugesia japonica and Phagocata vivida, were studied with light and electron microscope. Observation results were as follows. Except following details, fine structure and morphogenesis of the spermatogonia, primary spermatocyte, secondary spermatocyt spermatid and spermatozoon were consistant between the two species. The nucleus of primary spermatocyte of Dugesia japonica was surrounded with 36-38 microtubules, while that of Phagocata vivida with 40-42 microtubules. The C-shaped lamellar Golgi complex appeared in the spermatid cytoplasm of the former, while Straight-shaped lamellar Golgi complex in that of the latter. The four white spots were observed only in the nucleoplasm of matured spermatozoon in the latter, not in the former.

• Molecules and Cells
• /
• v.41 no.12
• /
• pp.1045-1051
• /
• 2018

The developmentally regulated GTP binding protein 2 (DRG2) is involved in the control of cell growth and differentiation. Here, we demonstrate that DRG2 regulates microtubule dynamics in HeLa cells. Analysis of live imaging of the plus-ends of microtubules with EB1-EGFP showed that DRG2 deficiency (shDRG2) significantly reduced the growth rate of HeLa cells. Depletion of DRG2 increased 'slow and long-lived' subpopulations, but decreased 'fast and short-lived' subpopulations of microtubules. Microtubule polymerization inhibitor exhibited a reduced response in shDRG2 cells. Using immunoprecipitation, we show that DRG2 interacts with tau, which regulates microtubule polymerization. Collectively, these data demonstrate that DRG2 may aid in affecting microtubule dynamics in HeLa cells.

• Advances in concrete construction
• /
• v.12 no.6
• /
• pp.491-497
• /
• 2021

Cell components play vital role within the cell when the cell under goes deformation. These components are microtubules, microfilaments and intermediate filaments. Intermediate filaments are like thread and are of different types. Like microtubules and microfilaments these components also undergo the deformation and their dynamics affected when change occurs within cell. In the present study, bending of intermediate filaments are studied keeping the nonlocal effects under consideration. It is observed that the nonlocal parameter has a great impact on the dynamics of intermediate filaments. This study is made by the application of Euler beam theory.

• Bulletin of the Korean Chemical Society
• /
• v.34 no.7
• /
• pp.1972-1984
• /
• 2013

Microtubules play an important role in intracellular transport, mobility, and particularly mitosis. Paclitaxel (Taxol$^{TM}$) and paclitaxel-like compounds have been shown to be anti-tumor agents useful for various human tumors. Paclitaxel-like compounds operate by stabilizing microtubules through interface binding at the interface between two ${\beta}$-tubulin monomers in adjacent protofilaments. In this paper we present the elucidation of the structural features of paclitaxel and paclitaxel-like compounds (e.g., epothilones) with microtubule stabilizing activities, and relate their activities to spatial and chemical features of the molecules. CATALYST program was used to generate three-dimensional quantitative structure activity relationships (3D-QSARs) resulting in 3D pharmacophore models of epothilone- and paclitaxel-derivatives. Pharmacophore models were generated from diverse conformers of these compounds resulting in a high correlation between experimental and predicted biological activities (r = 0.83 and 0.91 for epothilone and paclitaxel derivatives, respectively). On the basis of biological activities of the training sets, five- and four-feature pharmacophore hypotheses were generated in the epothilone and paclitaxel series. The validation of generated hypotheses was achieved by using twelve epothilones and ten paclitaxels, respectively, which are not in the training sets. The clustering (grouping) and merging techniques were used in order to supplement spatial restrictions of each of hypothesis and to develop more comprehensive models. This approach may be of use in developing novel inhibitor candidates as well as contributing a better understanding of structural characters of many compounds useful as anticancer agents targeting microtubules.

• Clinical and Experimental Reproductive Medicine
• /
• v.29 no.4
• /
• pp.229-236
• /
• 2002

Objective : The purpose of this study was to evaluate the effect of Cytochalasin B (CCB) on the cytoskeletal stability of mouse oocyte frozen by vitrification. Methods : Mouse oocytes retrieved from cycle stimulated by PMSG and hCG were treated by CCB and then vitrified in EFS-30. These oocytes were placed onto an EM grid and submerged immediately in liquid nitrogen. Thawing of the oocytes was carried out at room temperature for 5 seconds, then the EM grid was placed into 0.75 M, 0.5 M and 0.25 M sucrose at $37^{circ}C$ for 3 minutes, each. These oocytes were fixed in 4% formaldehyde for an hour and then washed in PPB for 15 minutes 3 times, then incubated in PPB containing anti-tubulin monoclonal antibody at $4^{circ}C$ overnight. And then, the oocytes were incubated with FITC-conjugated anti-mouse IgG and propidium iodide (PI) for 45 minutes. Pattern of microtubules and microfilaments of oocytes were evaluated with a confocal microscope. Results: The rate of oocytes containing normal microtubules and microfilaments was significantly decreased after vitrification. The rate of oocyte containing normal microtubules in CCB treated group was higher than those in non-treated group (53.7% vs. 48.9%), but the difference was not significant. The rate of oocyte containing normal microfilaments in CCB treated group was significantly higher than those in non-treated group (64.5% vs. 38.3%, p<0.05). Conclusion: Microfilaments stability could be improved by CCB treatment prior to vitrification. It is suggested that CCB treatment prior to vitrification improve stability of cytoskeleton and then increase success rate in IVF-ET program using vitrification and thawing oocyte.

• BMB Reports
• /
• v.40 no.1
• /
• pp.44-52
• /
• 2007

Kinesins, as a kind of microtubule-based motor proteins, have a conserved microtubule-binding site in their motor domain. Here we report that two homologous kinesins in Arabidopsis thaliana, KatB and KatC, contain a second microtubule-binding site in their tail domains. The prokaryotic-expressed N-terminal tail domain of the KatC heavy chain can bind to microtubules in an ATP-insensitive manner. To identify the precise region responsible for the binding, a serious of truncated KatC cDNAs encoding KatC N-terminal regions in different lengths, KatC1-128, KatC1-86, KatC1-73 and KatC1-63, fused to Histidine-tags, were expressed in E. coli and affinity-purified. Microtubule cosedimentation assays show that the site at amino acid residues 74-86 in KatC is important for microtubule-binding. By similarity, we obtained three different lengths of KatB N-terminal regions, KatB1-384, KatB1-77, and KatB1-63, and analyzed their microtubule-binding ability. Cosedimentation assays indicate that the KatB tail domain can also bind to microtubules at the same site as and in a similar manner to KatC. Fluorescence microscopic observations show that the microtubule-binding site at the tail domain of KatB or KatC can induce microtubules bundling only when the stalk domain is present. Through pull-down assays, we show that KatB1-385 and KatC1-394 are able to interact specifically with themselves and with each other in vitro. These findings are significant for identifying a previously uncharacterized microtubule-binding site in the two kinesin proteins, KatB and KatC, and the functional relations between them.

• Applied Microscopy
• /
• v.28 no.2
• /
• pp.193-205
• /
• 1998

The Urechis unicinctus sperm and spermatogenic cells prepared from the testis are investigated to identify $\alpha-tubulin$ of axoneme microtubules using mouse monoclonal $anti-\alpha-tubulin$ as the first Ab and Gold(10nm) conjugated goat anti-mouse IgG as the Ab marker. The Ag-Ab reaction analyzed excellently the localization of $\alpha-tubulin$ and the gold particles incorporated with the proximal and distal centrioles, manchette microtubules, and flagellum. The gold particles can be also observed in the spermatogenic cells while the cells are still in sperm ball which is composed of a somatic cell and spermatogenic cells. The sperm ball is the functional unit of sperm production in U unicinctus testis. The spermatids are developed from the spermatogenic cells in the sperm ball and released into the testis cavity through a cortical cytoplasmic opening. The spermatid architectures are similar with the mature sperm of the testis cavity in aspects of shape of discoid acrosome, degree of nuclear condensation and ring type of mitochondrion. However, the distal centriole connecting with the flagella can be observed from the mature sperm while the both proximal and distal centrioles reveal only in the spermatids. The proximal centriole is directly connected with nuclear outer membrane during the stage of nuclear condensation and oriented perpendicularly to the distal centriole whose axis coinciding with the longitudinal axis of the spermatozoon. There are indications that the distal centriole is intimately associated with the polymerization of the flagellum. The manchette microtubules appear during spermatid development but the mature sperm have round head and no conspicuous middle piece.

• Advances in nano research
• /
• v.10 no.1
• /
• pp.15-24
• /
• 2021

Microtubules (MTs) are the main part of the cytoskeleton in living eukaryotic cells. In this article, a mechanical model of MT buckling, considering the modified strain gradient theory, is analytically examined. The MT is assumed as a cylindrical beam and a new single variable trigonometric beam theory is developed in conjunction with a modified strain gradient model. The main benefit of the present formulation is shown in its new kinematic where we found only one unknown as the Euler-Bernoulli beam model, which is even less than the Timoshenko beam model. The governing equations are deduced by considering virtual work principle. The effectiveness of the present method is checked by comparing the obtained results with those reported by other higher shear deformation beam theory involving a higher number of unknowns. It is shown that microstructure-dependent response is more important when material length scale parameters are closer to the outer diameter of MTs. Also, it can be confirmed that influences of shear deformation become more considerable for smaller shear modulus and aspect ratios.

• Journal of Life Science
• /
• v.31 no.3
• /
• pp.280-286
• /
• 2021

Oryzalin is a herbicide that disrupts the arrangement of microtubules by binding to tubulin, thereby blocking the anisotropic growth of plant cells. Microtubules and microfilaments are cytoskeleton components that have been implicated in plant growth through their influence on the formation of cell walls. Microtubules also play roles in the sedimentation of amyloplasts in the root tip columella cells; this sedimentation is related to gravity sensing and results in downward root growth in the soil for absorption of water and minerals. However, the orientation of microtubules changes depending on the level of ethylene in plant cells. A recent study reported that oryzalin stimulated ethylene production via 1-aminocyclopropane-1-carboxylic acid (ACC) synthase and ACC oxidase and caused a concentration-dependent inhibition of root growth and gravitropic responses. The aim of the present study was to investigate the possibility that oryzalin-induced inhibition might be recovered by the application of inhibitors of ethylene production, such as 10-4 M cobalt ions and 10-8 M aminoethoxyvinylglycine (AVG). The inhibition of root growth and gravitropic response was overcome by 10-20% by an 8 hr treatment with cobalt ions or AVG. These results suggest that ethylene levels could regulate root growth and gravitropic responses in Arabidopsis.

• Journal of Life Science
• /
• v.31 no.2
• /
• pp.109-114
• /
• 2021

Oryzalin is a dinitroaniline herbicide that has been known to disrupt microtubules. Microtubules and microfilaments are components of cytoskeletons that are implicated in plant cell growth, which requires the synthesis of cellulose when cell walls elongate. In addition, microtubules are also involved in the sedimentation of statoliths, which regulate the perception of gravity in the columella cells of root tips. In this study, we investigated the effect of oryzalin on the growth and gravitropic response of Arabidopsis roots. The role of ethylene in oryzalin's effect was also examined using these roots. Treatment of oryzalin at a concentration of 10-4 M completely inhibited the roots' growth and gravitropic response. At a concentration of 10-6 M oryzalin, root growth was inhibited by 47% at 8 hr when compared to control. Gravitropic response was inhibited by about 38% compared to control in roots treated with 10-6 M oryzalin for 4 hr. To understand the role of oryzalin in the regulation of root growth and gravitropic response, we measured ethylene production in root segments treated with oryzalin. It was found that the addition of oryzalin stimulated ethylene production through the activation of ACC oxidase and ACC synthase genes, which are key components in the synthesis of ethylene. From these findings, it can be inferred that oryzalin inhibits the growth and gravitropic response of Arabidopsis roots by stimulating ethylene production. The increased ethylene alters the arrangement of the microtubules, which eventually interferes with the growth of the cell wall.