• The Korean Journal of Physiology and Pharmacology
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• v.8 no.4
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• pp.195-200
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• 2004

Ghrelin is a newly discovered peptide, which is released from the stomach and neurons in the hypothalamic arcuate nucleus (ARC), and potently stimulates growth hormone release and food intake. In the present study, we investigated the effect of ghrelin on $[Ca^{2+}]_i$ in thyroid FRTL-5 cells. Ghrelin (5 nM) increased $[Ca^{2+}]_i$ and TSH (1 unit/l) had an additive effect on $[Ca^{2+}]_i$ when extracellular normal solution was 1.1mM $Ca^{2+}$ containing Coon's modified Ham's F12 medium. When $Ca^{2+}-free$ medium containing 2 mM EGTA replaced the above normal solution, ghrelin also induced a similar rise in $[Ca^{2+}]_i$. In the middle of $[Ca^{2+}]_i$ increment by ghrelin, nifedipine $(1\;{\mu}M)$, nickel $(100\;{\mu}M)$ and $La^{3+}\;(100\;{\mu}M)$ had no effect on $[Ca^{2+}]_i$. After endoplasmic reticulum was depleted by cyclopiazonic acid $(CPA;10\;{\mu}M)$, ghrelin caused no visible change on $[Ca^{2+}]_i$ in $Ca^{2+}-free$/2 mM EGTA solution. These results suggest that ghrelin can increase $[Ca^{2+}]_i$ through endoplasmic reticulum in thyroid FRTL-5 cells.

• Journal of the Korean Ceramic Society
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• v.48 no.6
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• pp.584-588
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• 2011

In this work, effects of limestone powder on hydration of $C_3A-CaSO_4{\cdot}2H_2O$ system was discussed based on the XRD Quantitative analysis, and the possibility of Delayed Ettringite Formation was also discussed. The early hydration of $C_3A$ was delayed by addition of $CaCO_3$ powder. The delay effect was enhanced by increasing of $CaCO_3$ content and finer powder of $CaCO_3$ addition. After consumption of $CaSO_4{\cdot}2H_2O$, the reaction of $CaCO_3$ is started. Delayed Ettringite Formation would take place because monosulfoaluminate is not stable in presence of $CaCO_3$. In order to prevent the delayed ettringite formation in $C_3A-CaSO_4{\cdot}2H_2O-CaCO_3$ system, the reduction of monosulfoaluminate formation is important. Therefore, by increasing the amount of $CaCO_3$ addition and finer $CaCO_3$ powder addition, the delayed ettringite formation can be prevented.

• Applied Biological Chemistry
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• v.40 no.3
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• pp.202-208
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• 1997

In order to investigate the mechanisms of epithelial ion transports, microsomes of soybean roots were prepared and the activity of microsomal ATPases was measured by an enzyme-coupled assay. The effects of various ions were evaluated on the total activity of microsomal ATPases and the average activity was 190 nmol/min/mg protein in the control solution containing $10\;mM\;Na^+\;and\;120\;mM\;K^+$. The activities were increased to 150% and decreased to 63% of the control activity in the solution containing $130\;mM\;K^+$ without $Na^+$ and in the solution containing $130\;mM{\;}Na^+$ without $K^+$, respectively. In general, the activity of microsomal ATPase was increased by$K^+$ in a concentration-dependent manner The activity was also increased at lower pH and relatively higher activities were observed in the pH range of $6{\sim}7$. However, the activity was decreased at weak alkaline $pH\;and{\sim}80%$ of the activity was inhibited at pH 9. Since intracellular $Ca^{2+}$ has been known to control the activity of various enzymes, we have investigated the effects of intra-and extrarnicrosomal $Ca^{2+}$ on the activity of microsomal ATPases. The maximal activity was obtained at the extrarnicrosomal $Ca^{2+}$ concentrations below 1 nM. The activity was gradually decreased by increasing $‘Ca^{2+}’$ concentration and 50% inhibition was observed at ${\sim}500{\;}{\mu}M{\;}Ca^{2+}$. The increase in luminal $Ca^{2+}$ concentration also inhibited the activity of microsomal ATPase. When the influx of external $Ca^{2+}$ was induced by $Ca^{2+}$ ionophore A23187 treatment, the activity was decreased by 30%; however, it was recovered by EGTA-induced chelation of $Ca^{2+}$. These results suggest that the presence of $Ca^{2+}$ regulation sites on both cytoplasmi and luminal sides of microsomal ATPases.

• The Journal of Engineering Research
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• v.6 no.1
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• pp.97-109
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• 2004

The synthesis and crystal structure of amorphous calcium carbonate obtained from gas-liquid reaction of CaO-$C_2 H_5 OH$-$CO_2$ system according to change of added amount of calcium oxide by blowing $CO_2$ gas and reaction time using ethanol and ethylene glycol were investigated by electric conductivity, X-ray diffraction, and scanning electron microscope. The powdery or gelatinous phases were prepared by passing $CO_2$ gas at a flow rate of 1$\ell$/min into the suspensions containing 10~40g of CaO in mixing solutions 900ml of $C_2 H_5 OH$- and 100ml of ethylene glycol. By rapid filtration and drying the both phases at $60^{\circ}C$ under reduced pressure, the phases converted to the spherical vaterite and amorphous phase. The stable phase of amorphous calcium carbonate(ACC) was formed in the region pH 7-9 but the formation regions of amorphous phase were remarkably affected by pH in the mother liquor. It seems that a part of ACC changed into chain calcite as an intermediate products. The initial reactants prior to the formation of precipitated calcium carbonate is ACC. And ACC is unstable in the aqueous solution and crystallizes finally to calcite by the through-solution reaction. Especially ACC was produced or gelatinous phase which precipitated from the reaction of CaO-$C_2 H_5 OH$-$CO_2$ system.

• BMB Reports
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• v.34 no.3
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• pp.212-218
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• 2001

Although the blockage of a cell cycle by specific inhibitors of $Ca^{2+}/$calmodulin-dependent protein kinase II (CaMK-II) is well known, the activity profile of CaMK-II during the cell cycle in the absence of any direct effectors of the enzyme is unclear. The activity of native CaMK-II in NIH 3T3 cells was examined by the use of cell cycle-specific arresting and synchronizing methods. The total catalytic activity of CaMK-II in arrested cells was decreased about 30% in the M phase, whereas the $Ca^{2+}$-independent autonomous activity increased about 1.5-fold in the M phase and decreased about 50% at the G1/S transition. The in vivo phosphorylation level of CaMK-II was lowest at G1/S and highest in M. The CaMK-II protein level was unchanged during the cell cycle. When the cells were synchronized, the autonomous activity was increased only in M. These results indicate that the physiologically relevant portion of CaMK-II is activated only in M, and that the net activation of CaMK-II is required in mitosis.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.9 no.2
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• pp.163-170
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• 1997

Solubility on $(LiBr+CaCl_2)$ in water has been measured systematically and compared with those of pure LiBr. It has been observed that there exists optimum value of $CaCl_2(LiBr+CaCl_2)$ in solubility when total$(LiBr+CaCl_2)$ concentration is higher than 57wt%. As total concentration increases up to 65wt%, it is found that the optimum value also increases monotonically. From the experimental results, a master plot has been constructed, with which optimum ratio of LiBr to $CaCl_2$ can be found in terms of total concentration. Vapor pressure of $H_2O/(LiBr+CaCl_2)$ solution with optimum contents of $CaCl_2$ has been observed to be changed negligibly at relatiely low temperature. However, as temperature increases, it is found that increasement in vapor pressure is significant.

• The Korean Journal of Physiology
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• v.21 no.1
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• pp.1-12
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• 1987

There is evidence that the effect of extracellular $Ca^{2+}$ on heart rate is temperature-dependent: at $38^{\circ}C$ excess $Ca^{2+}$ induces positive chronotropic response, whereas at $30^{\circ}C$ there is no significant chronotropic effect of $Ca^{2+}$. The cause of this temperature-dependency, however, remains still unclear. Therefore, this study was undertaken to investigate the chronotropic effect of external $Ca^{2+}$ at different temperature in the isolated rabbit atria and in the small strips of SA node cut perpendicularly to crista terminalis. In the isolated atria, the $Ca^{2+}$ effect was temperature-dependent: at $35^{\circ}C$ excess $Ca^{2+}$ evoked positive chronotropic response, while at $30^{\circ}C$ there was no significant changes in sinus rate. On the contrary, in the small SA strips external $Ca^{2+}$ induced negative chronotropic effect. At $35^{\circ}C$ changes in $Ca^{2+}$ concentration from 2 to 4, 6, and 10 mM decreased the sinus rate by $2.7{\pm}1.6%$, $11.2{\pm}3.7%$ and $23.2{\pm}8.1%$ respectively. Lowering the temperature to $30^{\circ}C$, the negative chronotropic effect of $Ca^{2+}$ became greater. With intracellular microelectrodes transmembrane potential was recorded in the small SA strips at $30^{\circ}C$, $35^{\circ}C$ and $38^{\circ}C$. As temperature increased from 30 to $38^{\circ}C$, sinus rate was accelerated by $13/min/^{\circ}C$, $APD_{50}$(action ptential duration from peak to 50% repolarization) decreased by $5\;msec/^{\circ}C$, and amplitude of action potential was slightly decreased. With an increase in $Ca^{2+}$ concentrations from 0.5 to 6 mM, overshoot increased and MDP decreased. These $Ca^{2+}$ effects on the overshoot and MDP of action potentials were not altered by temperature. But the $Ca^{2+}$ effects on the rates of diastolic depolarization, systolic depolarization and repolarization were modified by temperature. Discrpancy of the chronotropic effects of $Ca^{2+}$ between isolated atria and small SA strips was discussed.

• Korean Journal of Agricultural Science
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• v.34 no.1
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• pp.37-46
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• 2007

This study was conducted to investigate the antler induction rate and production by artificial induction of antlerogenesis using $CaCl_2$ injection on both periosteum around area of horn development for the frontal bone of a female elk deer which do not have an antler. The results obtained from eleven deers for verifying effect of the female's antler induction on reproduction are as follows: The antler development induction by $CaCl_2$injection is higher on the treatments of 30 and 50% of $CaCl_2$ injection than those on the treatments of 15 %. The antler production is higher on the 30 % $CaCl_2$ injection than those of 15 and 50 % $CaCl_2$ injection. For 30 % $CaCl_2$ injection, the antler production is higher in 1.5 and 2.0 ml of % $CaCl_2$ injection than the other injection level. After the induction of antler development, the birth rate is not changed as of 75~100 %, while the regeneration rate of the antler which was not constant in approximately 45 % for five among eleven female deer. With these results, we assume that the injection concentration and amount of $CaCl_2$ injection are around 30 % and 1.5 and 2.0 ml level which can be not only most effective conditions for the antler induction rate and production, but also these conditions do not influence the reproduction during the period of the female elk's antler development induction.

• YAKHAK HOEJI
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• v.59 no.4
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• pp.158-163
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• 2015

Cardiac myocytes are subjected to fluid shear stress during each contraction and relaxation. Under pathological conditions, such as valve disease, heart failure or hypertension, shear stress in cardiac chamber increases due to high blood volume and pressure. The shear stress induces proarrhythmic longitudinal global $Ca^{2+}$ waves in atrial myocytes. In the present study, we further explored underlying cellular mechanism for the shear stress-induced longitudinal global $Ca^{2+}$ wave in isolated rat atrial myocytes. A shear stress of ${\sim}16dyn/cm^2$ was applied onto entire single myocyte using pressurized fluid puffing. Confocal $Ca^{2+}$ imaging was performed to measure local and global $Ca^{2+}$ signals. Shear stress elicited longitudinally propagating global $Ca^{2+}$ wave (${\sim}80{\mu}m/s$). The occurrence of shear stress-induced atrial $Ca^{2+}$ wave was eliminated by the inhibition of ryanodine receptors (RyRs) or inositol 1,4,5-trisphosphate receptors ($IP_3Rs$). In addition, pretreatment of phospholipase C (PLC) inhibitor U73122, but not its inactive analogue U73343, abolished the generation of longitudinal $Ca^{2+}$ wave under shear stress. Our data suggest that shear-induced longitudinal $Ca^{2+}$ wave may be induced by $Ca^{2+}$-induced $Ca^{2+}$ release through the RyRs which is triggered by $PLC-IP_3R$ signaling in atrial myocytes.

• The Korean Journal of Physiology and Pharmacology
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• v.3 no.2
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• pp.175-182
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• 1999

In the present study, the underlying mechanisms for diabetic functional derangement and insulin effect on diabetic cardiomyopathy were investigated with respect to sarcoplasmic reticulum (SR) $Ca^{2+}-ATPase$ and phospholamban at the transcriptional and translational levels. The maximal $Ca^{2+}$ uptake and the affinity of $Ca^{2+}-ATPase$ for $Ca^{2+}$ were decreased in streptozotocin-induced diabetic rat cardiac SR, however, even minimal amount of insulin could reverse both parameters. Levels of both mRNA and protein of phospholamban were significantly increased in diabetic rat hearts, whereas the mRNA and protein levels of SR $Ca^{2+}-ATPase$ were significantly decreased. In case of phospholamban, insulin treatment reverses these parameters to normal levels. Minimal amount of insulin could reverse the protein levels; however, it could not reverse the mRNA level of SR $Ca^{2+}-ATPase$ at all. Thus, the decreased SR $Ca^{2+}$ uptake appear to be largely attributed to the decreased SR $Ca^{2+}-ATPase$ level, which is further impaired due to the inhibition by the increased level of phospholamban. These results indicate that insulin is involved in the control of intracellular $Ca^{2+}$ in the cardiomyocyte through multiple target proteins via multiple mechanisms for the decrease in the mRNA for both SR $Ca^{2+}-ATPase$ and phospholamban which are unknown and needs further study.