• Animal cells and systems
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• v.1 no.1
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• pp.63-69
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• 1997

We have previously reported that NF-kB is involved in the regulation of nitric oxide synthase gene expression during differentiation of chick embryonic myoblasts. However, how NF-kB is timely activated during myogenesis remains elusive. One of the most prominent events in myogenesis is myoblast membrane fusion, which is accompanied with massive cytoskeletal reorganization. Here we show that the activity of NF-kB markedly increases in L6 rat myogenic cells that have just initiated morphological changes by treating nocodazole, a microtubule-disrupting agent. Furthermore, the induction of NF-kB activation was closely correlated with the myoblast fusion. In addition, a variety of agents that disrupt microtubules stimulated the myoblast fusion as well as the induction of NF-kB activation. In contrast, taxol, a microtubule-stabilizing agent, suppressed the induction of NF-kB activation and inhibited spontaneous differentiation of L6 cells as well. In addition, we found that the NF-KB in the cells consists of p50/p65 heterodimers. These results support the idea that reorganization of microtubule at early stages of differentiation plays a role as a signal for NF-KB activation during myogenesis.

• The Korean Journal of Zoology
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• v.34 no.4
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• pp.610-617
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• 1991

계배 근원세포의 분화 및 증식에 미치는 F3+의 영향을 조사하였다. 철이 없는 배양액은 근원 세포의 분화와 증식을 억제하는 것으로 나타났으며 , 따라서 근원세포의 분화에 철과 transferrin (Tf)은 필수적이다. 또한, 철 대신에 Co2+가 부착된 Tf가 첨가된 배양액에서도 근세포의 분화가 정상적으로 일어나는 것으로 나타났다. Lysosomotrophic amine(chloroquine, $\mu$M 수준;ammonium chloride, mM 수준)은 근세포의 분화와 증식을 억제시켰으며 , 근세포 분화의 철에 대한 의존성은 분화됨에 따라 둔화되었다. 세포내로의 T니 수송량은 MEM과 8102배양액에서 비슷하였고, 근세포가 분화됨에 따라 감소하였다. Lysosomotrophic azine은 최소한 3시간이 내에서는 세포내로 수송되는 Tf의 양에 영향을 미치지 못하였다.

• The Korean Journal of Zoology
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• v.26 no.1
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• pp.1-17
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• 1983

The synthesis of myosin, actin, tropomyosin and troponin in the cultured muscle cells of chick embryo during the differentiation were analyzed. The synthesis of myosin and actin were very active prior to the myoblast fusion while the troponin synthesis became active after the fusion. Tropomyosin was synthesized practically constantly throughout the culture period. Several proteins were detected in the muscle-conditioned medium strongly suggesting that the cells in culture released polypeptides which might act on the membrane of neighboring cells cells to initiate the fusion.

• Proceedings of the Zoological Society Korea Conference
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• 1996.10a
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• pp.172.2-172
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• 1996

No Abstract, See Full Text

• Proceedings of the Zoological Society Korea Conference
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• 1999.10b
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• pp.175.1-175
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• 1999

No Abstract, See Full Text

• Proceedings of the Zoological Society Korea Conference
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• 1999.10b
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• pp.176.1-176
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• 1999

No Abstract, See Full Text

• The Korean Journal of Zoology
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• v.28 no.3
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• pp.179-193
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• 1985

In order to find factors which are essential for the differentiation of chick embryonic myoblasts in culture, chick embryo extract was fractionated by ammonium sulfate or/and Sephadex G-75, and the effects of each fraction on the proliferation and fusion of the myoblasts were examined. The results obtained were as follows: (1) High concentration of embryo extract in the culture medium enhanced the cell proliferation and delayed the fusion of myoblasts. (2) The Sephadex G-75 fractions of embryo extract having proteins of molecular weight between 40,000 and 22,000 enhanced the proliferation and fusion of myoblasts when added to culture media. (3) The fraction of embryo extract precipitated in $60\\sim95%$ saturated ammonium sulfate solution enhanced evidently both the proliferation and fusion of myoblasts. Elution of this effective fraction by Sephadex G-75 showed similar elution profile and effects on the myoblast differentiation as those observed by Sephadex G-75 chromatography of the whole embryo extract, suggesting that the Sephadex fractions and ammonium sulfate fractions contain the same factors that enhance the proliferation and fusion of myoblasts.

• The Korean Journal of Zoology
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• v.36 no.3
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• pp.342-346
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• 1993

The protein level of cytoskeletons in cultured myoblasts was found to gradually decrease during the course of myogenesis. This decrease, however, could be prevented by treatiag the ceils with calpeptin (benzyloxycarbonyl-Leu-nLeu-H), a cell penetrating inhibitor of calpain. In contrast, E-64, which also is a potent inhibitor of calpain but can not be transported into the cells, showed little or no effect. In addition, the treatment of calpeptin was found to stabilize a number of specific cytoskeletal proteins from degradation but without any effect on the pattern of total cells proteins. Furthermore, calpeptin, but not E-64, blocked myoblast fusion in a dose-dependent manner. These results suggest that calpain is responsible for the myogenic time-dependent loss of cytoskeletal proteins and that the degradative process is associated with myoblast fusion. These results also suggest that the differential effects of the calpain inhibitors depend on the permeabIlity of the drugs across the cell membrane.

• The Korean Journal of Zoology
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• v.38 no.1
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• pp.78-86
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• 1995

Our previous report has suggested that the decrease of fibronectin level during mvogenesis is due to the decreased Bvailabilitv of receptor (matrix assembly receptor) for 29-kDa fragment of fibronectin. In the present study, we demonstrate that G protein and adenvlate cvclase system are involved in the regulation of fibronectin matrix assembly and that when fibronectin level in extracellular matrix decreases, the postmitotic fusion-capable cells emerge more frequently from the proliferative population. This proposal is based on the following observations. (1) Cholers toxin, which increases intracellular CAMP, caused a decrease in the ability of mvoblasts to incorporate fibronectin into extracellular matrix. (2) Cholera toxin decreased the proliferation of mvoblasts and Induced the precocious fusion. (3) decAMP, which was found to induce the precocious fusion and decrease the proliferation of myoblasts, decreased the fibronectin level in extracellular matrix and matrix assembly receptor for fibronectin- (4) RGOS, whlh inhibits the incorporation of fibronectin into extracellular matrix, induced the precocious fusion and reduced the proliferaton of mvoblasts. These results suggest that CAMP regulates the fibronectin levels in extracellular matrix and that the alteration of fibronectin level is involved in regulation of the proliferation and differentiation of chick embryonic mvoblasts.

• The Korean Journal of Zoology
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• v.33 no.1
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• pp.108-118
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• 1990

Fibronectin is a glycoprotein found in the extracellular matrix as well as in the serum, and has been known to exert pronouned effed on the myoblast fusion. Our previous studies have suggested that the decrease of fibronectin levels during myogenesis is due to the decreased availability of the receptor for the 28 kDa fragrnent of fibronetin. In the fusion-blocked myoblasts by EGTA, the levels of fibronetin and binding of 28 kDa fragment decreased but far less than the control level. In contrast, the levels of fibronetin and binding of 28 kDa fragment decreased to the control level in the myoblast released from the fusion block. On this account, we suggest that the decrease of fibronetin levels during myoblast fusion is closely associated with the loss or alteration of the receptor for 28 kDa fragment. Mild trypsin treatment decreased the binding of the 28 kDa fragment to the myoblasts significandy. Similarly, the presence of gangliosides in the binding media decreased the binding of the 28 kDa fragment in a dose-dependent manner. Furthermore, gel overlay of 125 I-28 kDa fragment on the SDS-PAGE of the myoblast homogenates revealed that the 28 kDa fragment bound to a 43 kDa protein and to gangliosides as well. These results suggest that myoblast fusion is correlated with decrease of the receptor for the 28 kDa fragment and that the receptor might be a glycoprotein that contains glyco-conjugate found in gangliosides.