• BMB Reports
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• 제55권11호
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• pp.528-534
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• 2022

Mitochondria are cellular organelles that perform various functions within cells. They are responsible for ATP production, cell-signal regulation, autophagy, and cell apoptosis. Because the mitochondrial proteins that perform these functions need Ca²⁺ ions for their activity, mitochondria have ion channels to selectively uptake Ca²⁺ ions from the cytoplasm. The ion channel known to play the most important role in the Ca²⁺ uptake in mitochondria is the mitochondrial calcium uniporter (MCU) holo-complex located in the inner mitochondrial membrane (IMM). This ion channel complex exists in the form of a complex consisting of the pore-forming protein through which the Ca²⁺ ions are transported into the mitochondrial matrix, and the auxiliary protein involved in regulating the activity of the Ca²⁺ uptake by the MCU holo-complex. Studies of this MCU holo-complex have long been conducted, but we didn't know in detail how mitochondria uptake Ca²⁺ ions through this ion channel complex or how the activity of this ion channel complex is regulated. Recently, the protein structure of the MCU holo-complex was identified, enabling the mechanism of Ca²⁺ uptake and its regulation by the MCU holo-complex to be confirmed. In this review, I will introduce the mechanism of action of the MCU holo-complex at the molecular level based on the Cryo-EM structure of the MCU holo-complex to help understand how mitochondria uptake the necessary Ca²⁺ ions through the MCU holo-complex and how these Ca²⁺ uptake mechanisms are regulated.

• 한국세라믹학회지
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• 제47권3호
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• pp.244-248
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• 2010

Porous calcium phosphates were successfully fabricated by using a cuttlefish bone. The cuttlefish bone, which is composed of $CaCO_3$, showed a special porous microstructure containing uniform-sized voids. In this study, the pre-forms infiltrated distilled phosphoric acid were sintered at $1200^{\circ}C$ in an air atmosphere. The porous microstructure of the pre-forms was kept their original pattern after sintering with a synthesis of calcium phosphate. The obtained porous calcium phosphate, sintered at $1200^{\circ}C$ for 3 h at 17% concentration of phosphoric acid, showed uniform open pores of 150 ${\mu}m$ in size and $\beta$-TCP phase in the XRD patterns. Above 16% concentration, CaO phase, derived from the decomposition of $CaCO_3$, decreased gradually in the sintered samples, and the measured Ca/P ratios of the samples prepared from 16% and 18% concentration were 1.67 and 1.43, which are close to stoichiometric HA (1.66) and $\beta$-TCP (1.50).

• Journal of Animal Science and Technology
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• 제64권5호
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• pp.871-884
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• 2022

Two experiments were conducted to evaluate the effects of calcium (Ca) levels in weanling pigs (Landrace × Yorkshire × Duroc). In experiment 1, one hundred and eighty weanling pigs were randomly allotted to one of the three treatments. The treatments were low (Ca 0.60% in phase 1 and 0.50% in phase 2), standard (Ca 0.72% in phase 1 and 0.66% in phase 2), and high (Ca 0.84% in phase 1 and 0.72% in phase 2). In experiment 2, hundred and forty weanling pigs were randomly assigned to one of four treatments differing in Ca levels (high and low) and sources (CaCl₂ and CaCO₃) in a 2 × 2 factorial arrangement. There were 10 pigs per replicate in both experiments, with 6 replicates in each treatment, and they were conducted in two phases (phase 1, days 0-14; phase 2, days 15-28). In experiment 1, body weight (BW), average daily gain (ADG), and growth to feed ratio (G/F) increased as the Ca level decreased (p < 0.05). P digestibility was higher in the low-Ca diet group than in the high-Ca diet group (p <0.05). In experiment 2, the final BW, ADG, and G/F increased in the CaCl₂ diet group compared with the case in the CaCO₃ diet group (p < 0.05). The digestibility of crude protein (CP), Ca, and P was higher in the CaCl₂ diet group than in the CaCO₃ diet group (p < 0.05). Cl^- levels were higher in the CaCl₂ diet group than in the CaCO₃ diet group (p < 0.05). The bicarbonate (HCO_3-), base excess (BE), and electrolyte balance (EB) levels were lower in the CaCl₂ diet group than in the CaCO₃ diet group (p < 0.05). Hematocrit increased as the Ca level decreased (p < 0.05). The HCO_3- interacted with the Ca sources and thus, affected the Ca levels (p < 0.05). Bone ash, Ca, and P were downregulated in the low-Ca diet group compared with the case in the high-Ca diet group. Overall, the low dietary Ca supplementation led to greater growth performance. Furthermore, CaCl₂ appeared to be a better Ca source than CaCO₃ because of the greater digestibility of CP, Ca, and P, and improved EB.

• 한국세라믹학회지
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• 제29권4호
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• pp.65-65
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• 1992

12Ce-TZP의 소결에 미치는 CaO의 역할에 대하여 연구하였다. CaO의 첨가는 Ce-TZP의 격자결함구조와 확산의 율속종인 cerium과 zirconium 이온의 확산계수를 변화시켜 치밀화를 촉진시킨다. CaO는 또한 소결과정중 결정립 성장을 억제하며, 이는 소결과정중 임계 이동시 입계로부터의 기공의 분리를 방지함과 동시에 기공으로부터 입계로의 공격자의 빠른 확산을 유지시킴으로써 이론밀도까지의 소결을 가능하게 한다. Ce-TZP의 결정립 성장 억제는 calcium의 입계편석에 의한 입계 이동도의 감소에 의하며, calcium의 입계편석을 AES 분석으로 확인하였다.

• 천문학회보
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• 제39권2호
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• pp.47.1-47.1
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• 2014

The calcium infrared triplet (CaT) is one of the prominent absorption features in the infrared wavelength regime. Recently, this absorption feature has been getting attention in the prediction of metallicity of stellar populations because of its strong sensitivity to the calcium abundance and metallicity of a star. However, we find that measuring metallicity directly from CaT is very dangerous because the formation mechanism of CaT is very inefficient in the cool stars which are abundant in metal-rich populations. This characteristics of CaT make the CaT-metallicity relation to converge around ~ $8{\AA}$ in the metal-rich regime. Our results suggest that, because of the converging CaT-metallicity relation in the metal-rich regime, the metallicity of simple stellar populations greater than [Fe/H]~-0.5 is unreliable when the linear conversion between CaT and metallicity is applied to derive metallicity. Based on these results, we suggest that CaT is not a good metallicity indicator for the metal-rich stellar populations.

• 원예과학기술지
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• 제33권4호
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• pp.525-534
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• 2015

The effects of aqueous calcium oxide (CaO) treatment on the quality characteristics and shelf life of mulberry (Morus alba L.) were investigated. Mulberry fruits were immersed in 0, 0.5, 1, and $2g{\cdot}L^{-1}$ CaO solutions for 0, 1, 3, 6, and 12 min. Mulberries were then rinsed with potable tap water for 1 min and stored at $-1^{\circ}C$ for 14 days. CaO treatment was effective at promoting the retention of titratable acid, pH, and ascorbic acid as well as total flavonoid contents. CaO concentration and treatment time were significant factors affecting the sensory qualities of the fruits, including off-odor, flavor, and texture. For shelf life determinations, the total bacterial count was reduced by CaO treatment so that the samples treated with $1g{\cdot}L^{-1}$ CaO for 12 min had bacterial levels at 14 days comparable to those of the control at 4 day, and no coliform group was detected after CaO treatment. These results indicate that calcium oxide treatment is a promising approach for the preservation of mulberry fruit.

• International Journal of Oral Biology
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• 제40권4호
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• pp.211-216
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• 2015

Nitric Oxide (NO) is an important signaling molecule in the nociceptive process. Our previous study suggested that high concentrations of sodium nitroprusside (SNP), a NO donor, induce a membrane hyperpolarization and outward current through large conductances calcium-activated potassium ($BK_{ca}$) channels in substantia gelatinosa (SG) neurons. In this study, patch clamp recording in spinal slices was used to investigate the sources of $Ca^{2+}$ that induces $Ca^{2+}$-activated potassium currents. Application of SNP induced a membrane hyperpolarization, which was significantly inhibited by hemoglobin and 2-(4-carboxyphenyl) -4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide potassium salt (c-PTIO), NO scavengers. SNP-induced hyperpolarization was decreased in the presence of charybdotoxin, a selective $BK_{Ca}$ channel blocker. In addition, SNP-induced response was significantly blocked by pretreatment of thapsigargin which can remove $Ca^{2+}$ in endoplasmic reticulum, and decreased by pretreatment of dentrolene, a ryanodine receptors (RyR) blocker. These data suggested that NO induces a membrane hyperpolarization through $BK_{ca}$ channels, which are activated by intracellular $Ca^{2+}$ increase via activation of RyR of $Ca^{2+}$ stores.

• BMB Reports
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• 제46권12호
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• pp.600-605
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• 2013

Interplay between calcium ions ($Ca^{2+}$) and reactive oxygen species (ROS) delicately controls diverse pathophysiological functions of vascular smooth muscle cells (VSMCs). However, details of the $Ca^{2+}$ and ROS signaling network have been hindered by the absence of a method for dual measurement of $Ca^{2+}$ and ROS. Here, a real-time monitoring system for $Ca^{2+}$ and ROS was established using a genetically encoded hydrogen peroxide indicator, HyPer, and a ratiometric $Ca^{2+}$ indicator, fura-2. For the simultaneous detection of fura-2 and HyPer signals, 540 nm emission filter and 500 nm~ dichroic beamsplitter were combined with conventional exciters. The wide excitation spectrum of HyPer resulted in marginal cross-contamination with fura-2 signal. However, physiological $Ca^{2+}$ transient and hydrogen peroxide were practically measurable in HyPer-expressing, fura-2-loaded VSMCs. Indeed, distinct $Ca^{2+}$ and ROS signals could be successfully detected in serotonin-stimulated VSMCs. The system established in this study is applicable to studies of crosstalk between $Ca^{2+}$ and ROS.

• 한국세라믹학회지
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• 제53권6호
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• pp.670-675
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• 2016

Calcium phosphate crystallites were prepared by wet chemical method for use in artificial bone. In order to obtain ${\beta}$-tricalcium phosphate (TCP), nano-crystalline calcium phosphate (CaP) was precipitated at $37^{\circ}C$ and at $pH5.0{\pm}0.1$ under stirring using highly active $Ca(OH)_2$ in DI water and an aqueous solution of $H_3PO_4$. The precipitated nano-crystalline CaP solution was kept at $90^{\circ}C$ for the growth of CaP crystallites. Through the growing process of CaP crystallites, we were able to obtain various sizes of rectangular CaP crystallites according to the crystal growing times. Dry nano-crystalline CaP powders at $37^{\circ}C$ were mixed with dry macro-crystalline CaP crystallites and the shaped mixture sample was fired at $1150^{\circ}C$ to make a ${\beta}-TCP$ block. Several tens of nm powders were uniformly coated on the surface, which was comprised of powders of several tens of ${\mu}m$, using a vibrator. The mixing ratio between the nanometer powders and the micrometer powders greatly affected the mechanical strength of the mixture block; the most appropriate ratio of these two materials was 50 wt% to 50 wt%. The sintered block showed improved mechanical strength, which was caused by the solid state interaction between the nano-crystalline ${\beta}-TCP$ and the macro-crystalline ${\beta}-TCP$.

• 한국세라믹학회지
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• 제29권1호
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• pp.74-82
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• 1992

Ultra-fine calcium phosphate powders were synthesized by the reaction of Ca(OH)2 suspension with various phosphoric aqueous solutions such as (NH4)2HPO4, H4P2O7 and H3PO4, and the characterization of powders was examined for each synthetic condition. When (NH4)2HPO4 and H3PO4 were used, hydroxyapatite powders with poor crystallinity were obtained. In the case of H4P2O7, amorphous calcium phosphate was obtained up to 0.3 mol/ι Ca(OH)2 suspension, but above the concentration, poor crystalline hydroxyapatite was produced. Crystalline phases of powders heat-treated at 80$0^{\circ}C$ were hydroxyapatite, $\beta$-tricalcium phosphate and $\beta$-tricalcium phosphate for the case of (NH4)2HPO4, H4P2O7 and H3PO4, respectively. SEM observation revealed that the shapes of synthesized powders were vigorously agglomerated spherical with the size below 100 nm, but TEM observation revealed that primary shapes of particles were rod for (NH4)2HPO4 and H3PO4 and were sphere for H4P2O7. There was no dependence of the concentration of Ca(OH)2 suspension. In the case that reaction temperature and pH of the suspension were raised, the inclination to the hydroxyapatite were remarkable. The amorphous calcium phosphate synthesized in this experiment contained water about 20% , and was crystallized to $\beta$-tricalcium phosphate at 69$0^{\circ}C$.