• Asian-Australasian Journal of Animal Sciences
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• v.11 no.6
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• pp.713-717
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• 1998

The synergistic effect of fetal calf serum (FCS) and chicken embryo extract (CEE) on protein synthesis of chicken embryo myoblasts was examined. Myoblasts were derived from chicken embryo cultured for 14 days by trypsin digestion and cultured in 5% $CO^2/95%$ air at $37^{\circ}C$. When myoblasts were cultured at the low level of cell density (20-50% of well), CEE enhanced the ability of FCS to stimulate protein synthesis of myoblasts. However, there was no significant effect of CEE to stimulate protein synthesis of myoblasts cultured at high level of cell density (100% of well).

• The Korean Journal of Physiology and Pharmacology
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• v.23 no.6
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• pp.519-528
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• 2019

Mitochondrial dysfunction is closely associated with reactive oxygen species (ROS) generation and oxidative stress in cells. On the other hand, modulation of the cellular antioxidant defense system by changes in the mitochondrial DNA (mtDNA) content is largely unknown. To determine the relationship between the cellular mtDNA content and defense system against oxidative stress, this study examined a set of myoblasts containing a depleted or reverted mtDNA content. A change in the cellular mtDNA content modulated the expression of antioxidant enzymes in myoblasts. In particular, the expression and activity of glutathione peroxidase (GPx) and catalase were inversely correlated with the mtDNA content in myoblasts. The depletion of mtDNA decreased both the reduced glutathione (GSH) and oxidized glutathione (GSSG) slightly, whereas the cellular redox status, as assessed by the GSH/GSSG ratio, was similar to that of the control. Interestingly, the steady-state level of the intracellular ROS, which depends on the reciprocal actions between ROS generation and detoxification, was reduced significantly and the lethality induced by $H_2O_2$ was alleviated by mtDNA depletion in myoblasts. Therefore, these results suggest that the ROS homeostasis and antioxidant enzymes are modulated by the cellular mtDNA content and that the increased expression and activity of GPx and catalase through the depletion of mtDNA are closely associated with an alleviation of the oxidative stress in myoblasts.

• The Korean Journal of Zoology
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• v.29 no.4
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• pp.294-306
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• 1986

In order to find out whether myoblast cells release into the culture medium any substances that induce or promote the fusion of myoblasts, chick embryonic myoblasts were cultured and the cultured medium (muscle-conditioned medium, MCM) was collected. The MCM was then added to the newly cultured myoblasts to examine if it has fusion-promoting activity. The MCM was also analyzed for its protein content before and after its addition to the second culture. The MCM apparently showed fusion-promoting activity when applied to unfused young myoblasts, suggesting that it contained substances that promote the fusion and that had been released from cells fo the previous culture. Analysis of proteins in the myoblasts and in the MCM suggested that the released protein was absorbed by or tightly bound to myoblasts of the second culture. One of the released proteins of about 175 kilodalton was degraded to a polypeptide of approximately 145 kilodalton, which appeared to act upon the membrane proteins of unfused myoblasts so as to stimulate their membrane to fuse with neighboring cells.

• The Journal of Internal Korean Medicine
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• v.29 no.1
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• pp.243-257
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• 2008

Myostatin, a negative regulator of myogenesis, is shown to function by controlling the proliferation of myoblasts. In this study we show that myostatin is an inhibitor of myoblast differentiation and that this inhibition is mediated through Smad 3. To determine MyoD expression by Dodamtang treatment, we compared the expression pattern of $C_{2}C_{12}$ mouse myoblasts that constitutively express myostatin with control cells. In vitro, increasing concentrations of Dodamtang reversibly prevented the myogenic blockage of myoblasts by myostatin expression. ELISA assay, Western and confocal analysis indicated that treatment of Dodamtang to the low serum culture media increased the levels of MyoD leading to the inhibition of myogenic differentiation by myostatin. The stable transfection of $C_{2}C_{12}$ myoblasts with myostatin expressing constructs did rescue MyoD-induced myogenic differentiation. Consistent with this, the treatment of Dodamtang rescued the expression of a MyoD in $C_{2}C_{12}$ myoblasts treated with myostatin. Taken together, these results suggest that induction of MyoD by Dodamtang inhibits myostatin activity and expression via SMAD3 resulting in the rescue of the myoblasts to differentiate into myotubes. Thus we propose that myostatin action by Dodamtang plays a critical role in myogenic differentiation and that the muscular hyperplasia and hypertrophy seen in animals that blockage of functional myostatin is because of deregulated proliferation and differentiation of myoblasts.

• 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.

• Biomedical Science Letters
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• v.12 no.3
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• pp.201-208
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• 2006

PI3-kinase activity through p85, the regulatory subunit of class IA PI3-kinase, is indispensable for the growth, differentiation, and survival of skeletal muscle cells, but little is known about the function of other regulatory subunits such as p55 and p50. We examined the subcellular localization and the expression of the regulatory subunits of class IA PI3-kinase in L6 myoblasts. Both p55 and p50 as well as p85 were expressed in L6 myoblasts. Whereas p85 was localized at both cytosolic and nuclear tractions, p55 and p50 were localized at only the nuclear traction. During the differentiation of L6 myoblasts, the protein concentrations of both p55 and p50 were decreased but that of p85 was not significantly changed. Menadione-induced oxidative stress induced the translocation of p85 from cytosol to nucleus and the increase of p55 expression. These results suggest that the regulatory subunits of class IA PI3-kinase play an important role in L6 myoblasts.

• Animal cells and systems
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• v.12 no.1
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• pp.35-39
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• 2008

Menadione induced cell death in cultured C2 myoblasts. By screening synthetic peptide libraries composed of random sequence of hexapeptides, we identified the hexa-peptides pool of(Ala/Ile)-(Ile/Met)-Val-Ile-Asp-(Met/Ser)-$NH_2$ that protected the myoblasts against menadioneinduced cell death. Pre-incubation with the hexapeptide pool reduced the number of cells detached from culture dish substrate and increased the ratio of relative viability against menadione. In addition, the peptides strongly increased the expression of Bcl-2, an anti-apoptotic protein. These results suggest that the hexapeptides might enhance the resistance to cell death against menadione by increasing the expression of Bcl-2.

• Asian-Australasian Journal of Animal Sciences
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• v.20 no.7
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• pp.1115-1119
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• 2007

This study was conducted to determine the difference between satellite cells (porcine) and myoblasts (C2C12) in their differentiation under the influence of 2, 4-thiazolidindion. C2C12 myoblast cells and porcine satellite cells (isolated from 10 d old $Landrace{\times}Duroc$ piglets) were grown to absolute confluency. Post confluent cells (day 0) were further exposed to adipogenic induction medium along with 2, 4-thiazolidindion ($8{\mu}M$) for 2 d. Thereafter, cells were exposed to 2, 4-thiazolidindion alone every 2 d till day 10 and analysed. The control was cultured in differentiation medium without any treatment. Increased (p<0.05) expression of transcriptional factors i.e. C/EBP-${\alpha}$ and PPAR-${\gamma}$ and transition of cells to adipocyte morphology was noticed from 2 d and 4 d onwards in satellite cells (Porcine) and myoblasts (C2C12) respectively. Myogenesis was observed to be suppressed completely in case of satellite cells compared to myoblasts in response to 2, 4-thiazolidindion. Pax-7 (transcriptional factor) appeared as a sole entity to satellite cells only, as it was not identified in case of myoblasts. Although both the cells were converting to adipoblasts, the degree of their conversion was different in response to 2, 4-thiazolidindion. Therefore, the hypothesis that satellite cells contribute various domains to the growing myoblasts appeared obscured and found to be dependent on the proliferative energy/or degree of fusion. However, it revealed satellite cells as currency to myoblasts/muscle.

• The Korean Journal of Physiology and Pharmacology
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• v.22 no.6
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• pp.697-703
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• 2018

Myoblast fusion depends on mitochondrial integrity and intracellular $Ca^{2+}$ signaling regulated by various ion channels. In this study, we investigated the ionic currents associated with $[Ca^{2+}]_i$ regulation in normal and mitochondrial DNA-depleted(${\rho}0$) L6 myoblasts. The ${\rho}0$ myoblasts showed impaired myotube formation. The inwardly rectifying $K^+$ current ($I_{Kir}$) was largely decreased with reduced expression of KIR2.1, whereas the voltage-operated $Ca^{2+}$ channel and $Ca^{2+}$-activated $K^+$ channel currents were intact. Sustained inhibition of mitochondrial electron transport by antimycin A treatment (24 h) also decreased the $I_{Kir}$. The ${\rho}0$ myoblasts showed depolarized resting membrane potential and higher basal $[Ca^{2+}]_i$. Our results demonstrated the specific downregulation of $I_{Kir}$ by dysfunctional mitochondria. The resultant depolarization and altered $Ca^{2+}$ signaling might be associated with impaired myoblast fusion in ${\rho}0$ myoblasts.

• Journal of Life Science
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• v.22 no.10
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• pp.1316-1323
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• 2012

The present study was conducted to investigate whether myoblasts can be transdifferentiated into adipocytes by ectopic expression of adipogenic transcription factors, including peroxisome proliferator-activated receptor-${\gamma}$ ($PPAR{\gamma}$), CCAAT/enhancer-binding protein-${\alpha}$ (C/$EBP{\alpha}$), sterol regulatory element binding protein-1c (SREBP1c), and Krueppel-like factor 5 (KLF5), in primary bovine satellite cells. Transcription factors were transiently transfected into primary bovine myoblasts, and the cells were cultured with adipogenic differentiation medium for 2 days and then cultured on growth medium for an additional 8 days. Ectopic expression of $PPAR{\gamma}$ or C/$EBP{\alpha}$ alone was insufficient to induce adipogenesis in myoblasts. However, overexpression of both $PPAR{\gamma}$ and C/$EBP{\alpha}$ in myoblasts was able to induce adipogenic transdifferentiation as indicated by the appearance of mature adipocytes, the induction of adipogenic gene expressions, and the suppression of myogenic gene expressions. In addition, KLF5 and $PPAR{\gamma}$ co-transfected bovine myoblasts were converted to adipocytes but not in cells transfected with only KLF5 expression vector. Overexpression of SREBP1c alone was sufficient to induce transdifferentiation from myoblasts into adipocytes. These results demonstrate that primary bovine satellite cells can be transdifferentiated into adipocytes either by single ectopic expression or combined expression of adipogenic transcription factors in a culture system.