• Food Science of Animal Resources
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• v.34 no.3
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• pp.307-315
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• 2014

pH adjustment would be of advantage in improving the water holding capacity of muscle proteins. The objective of this study was to evaluate the addition of fish sarcoplasmic protein (SP) solution, which was adjusted to pH 3.0 or 12.0, neutralized to pH 7.0, and lyophilized to obtain the acid- and alkaline-treated SP samples, on the functional properties of the chicken myofibrillar protein induced by microbial transglutaminase (MTG). The solubility of alkaline-treated SP was higher than that of the acid counterpart; however, those values of the two pH-treated samples were lower than that of normal SP (p<0.05). All SP solutions were mixed with myofibrillar proteins (MP) extracted from chicken breast, and incubated with MTG. The shear stresses of MP with acid- and alkaline-treated SP were higher than that of normal SP. The thermal stability of MP mixture reduced upon adding SP, regardless of the pH treatment. The breaking force of MP gels with acid-treated SP increased more than those of alkaline-treated SP, while normal SP showed the highest value. The MP gel lightness increased, but cooking loss reduced, with the addition of SP. Smooth microstructure of the gel surface was observed. These results indicated that adjusting the pH of SP improved the water holding capacity of chicken myofibrillar proteins induced by MTG.

• Food Science of Animal Resources
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• v.41 no.4
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• pp.650-663
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• 2021

The objective of this study was to examine the relationship between meat quality attributes and the changes of sarcoplasmic protein acetylation and myofibrillar protein acetylation in lamb longissimus thoracis et lumborum muscles at different postmortem phases. Protein acetylation, color, pH, shear force, myofibril fragmentation index and cooking loss were measured. The total level of acetylated sarcoplasmic proteins showed a negative relation with pH, a positive relation with a^*, b^* and cooking loss at the pre-rigor phase. Sarcoplasmic proteins acetylation affected postmortem pH by regulating glycolysis, which in turn affects color and cooking loss. The total level of acetylated myofibrillar proteins showed a positive relation with shear force at the pre-rigor phase. Myofibrillar proteins acetylation affected meat tenderness by regulating muscle contraction. This study indicated that acetylation played a regulatory role of meat color, water-holding capacity, and tenderization process at early postmortem.

• Proceedings of the Korean Biophysical Society Conference
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• 1999.06a
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• pp.29-29
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• 1999

Diabetic cardiomyopathy has been suggested to be caused by the intracellular Ca$\^$2＋/ overload in the myocardium. We have investigated the possible mechanism of the functional defect of cardiac sarcoplasmic reticulum (SR) in diabetic rats with respect to Ca$\^$2＋/-ATPase and phospholamban (PLB) at the transcriptional and translational levels.(omitted)

• BMB Reports
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• v.46 no.5
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• pp.237-243
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• 2013

Heart failure is one of the leading causes of sudden death in developed countries. While current therapies are mostly aimed at mitigating associated symptoms, novel therapies targeting the subcellular mechanisms underlying heart failure are emerging. Failing hearts are characterized by reduced contractile properties caused by impaired $Ca^{2+}$ cycling between the sarcoplasm and sarcoplasmic reticulum (SR). Sarcoplasmic/endoplasmic reticulum $Ca^{2+}$ ATPase 2a (SERCA2a) mediates $Ca^{2+}$ reuptake into the SR in cardiomyocytes. Of note, the expression level and/or activity of SERCA2a, translating to the quantity of SR $Ca^{2+}$ uptake, are significantly reduced in failing hearts. Normalization of the SERCA2a expression level by gene delivery has been shown to restore hampered cardiac functions and ameliorate associated symptoms in pre-clinical as well as clinical studies. SERCA2a activity can be regulated at multiple levels of a signaling cascade comprised of phospholamban, protein phosphatase 1, inhibitor-1, and $PKC{\alpha}$. SERCA2 activity is also regulated by post-translational modifications including SUMOylation and acetylation. In this review, we will highlight the molecular mechanisms underlying the regulation of SERCA2a activity and the potential therapeutic modalities for the treatment of heart failure.

• BMB Reports
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• v.51 no.8
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• pp.378-387
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• 2018

Skeletal muscle contracts or relaxes to maintain the body position and locomotion. For the contraction and relaxation of skeletal muscle, $Ca^{2+}$ in the cytosol of skeletal muscle fibers acts as a switch to turn on and off a series of contractile proteins. The cytosolic $Ca^{2+}$ level in skeletal muscle fibers is governed mainly by movements of $Ca^{2+}$ between the cytosol and the sarcoplasmic reticulum (SR). Store-operated $Ca^{2+}$ entry (SOCE), a $Ca^{2+}$ entryway from the extracellular space to the cytosol, has gained a significant amount of attention from muscle physiologists. Orai1 and stromal interaction molecule 1 (STIM1) are the main protein identities of SOCE. This mini-review focuses on the roles of STIM proteins and SOCE in the physiological and pathophysiological functions of skeletal muscle and in their correlations with recently identified proteins, as well as historical proteins that are known to mediate skeletal muscle function.

• The Korean Journal of Physiology and Pharmacology
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• v.4 no.5
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• pp.417-425
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• 2000

The underlying mechanism commonly applicable for both the positive and negative force-frequency relationships (FFR) was pursued in left atria (LA) of rat and rabbit. The species differences in the roles of $Na^+/Ca^{2+}$ exchanger and sarcoplasmic reticulum (SR), which are major intracellular $Ca^{2+}$ regulatory mechanisms in the heart, were examined in the amplitude accommodation to the frequency that changed from 3 Hz to the variable test frequencies for 5 minutes in the electrically field stimulated left atria (LA) of rat and rabbit. Norepinephrine strongly increased the frequency-related amplitude accommodation in both of rat and rabbit LA, while monensin, oubain or the reduced $Na^+$ and 0 mM $Ca^{2+}$ containing Tyrode solution increased the frequency-related amplitude accommodation only in the rabbit LA. Monenisn was also able to increase the frequency-related amplitude accommodation only in 1-day old rat LA but not in 4-week old rat LA that had 75% less $Na^+/Ca^{2+}$ exchanger with 97% higher SR than 1-day old rat LA. Taken together, it is concluded that the differences in the prevalence between myocardial $Na^+/Ca^{2+}$ exchanger and SR in the amplitude accommodation to the frequency-change determine the difference in the FFR between rat and rabbit heart.

• The Korean Journal of Physiology
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• v.21 no.2
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• pp.179-189
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• 1987

Since it has been known that ryanodine has a potent negative inotropic effect on the cardiac muscle contractility (Jenden and Fairhurst, 1968), ryanodine has been a subject of intensive research (Frank and Sleator, 1975; Jones et al, 1978; Sutko et al, 1985). However, the underlying mechanism for the ryanodine dependent negative inotropic effect is still uncertain. In this study, the effects of ryanodine on the generation and relaxation of contracture due to Na-withdrawal and on the force-frequency relationship of heart muscles isolated from rats and guinea pigs were measured in an effort to understand the underlying mechanism of the ryanodine-induced negative inotropy. Results are summerized as follows: 1 ) Ryanodine significantly reduced the contractility of heart muscles produced at low frequency of stimulation, but showed a little effect on the contractility at high frequency stimulation. 2) Ryanodine, at the concentrations ranging from $10^{-6}\;M$ to $10^{-8}\;M$, had no significant effect on the Na-dependent relaxation of Na-withdrawl contracture. 3) Ryandoine significantly reduced the amplitude of the Na-withdrawl contracture, and this inhibitory effect was reinforced by procaine, antiagonized by caffeine and high potassium. From these results, it may be concluded that the negative inotropic effect of ryanodine is mainly due to an inhibition of calcium release from sarcoplasmic reticulum.

• The Korean Journal of Zoology
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• v.14 no.2
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• pp.43-56
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• 1971

The Ca uptake by the fragmented sarcoplasmic reticulum of the rabbit skeletal muscle was measured under various concentrations of K, Mg, Caffeine, procaine and quinine. The ATPase activity of this reticular membrane was measured under the same conditions simultaneously. The saturation of Ca uptake was almost completed within 1 minute. The Ca uptake was inhibited by high concentrations of K (above 50 mM) and Mg (above 1 mM)in the absence of ATP. When ATP is present, however, the Ca uptake did not reflect the concentration of K, while it increased greatly as the concentration of Mg was increased. Caffeine and procaine caused the inhibition of Ca uptake in the presence of ATP, but quinine did not. The ATPase activity of the membrane was little affected by the concentration of K, while it was enhanced in the presence of Mg. Caffeine, procaine and quinine did not influence the ATPase activity.

• The Korean Journal of Zoology
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• v.20 no.2
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• pp.101-107
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• 1977

The effects of sodium azide, cAMP, G-strophanthin and dicumarol on the ATP-ase activity and Ca uptake of the fragmented sarcoplasmic reticulum of skeletal muscle were studied and the effects were compared with respect to the enzymatic activity and Ca transport. Sodium azide (0.05 mM) and G-strophanthin (0.25mM) caused no inhibition on either ATPase activity or Ca uptake. cAMP($1\\times10^{-6}\\sim5\\times10^{-4}$) had no effect on ATPase activity while inhibited Ca uptake. Dicumarol (0.05 mM) did not inhibit ATPase activity but caused a decreased Ca uptake of heavier fraction (8,000-12,000xG) of the reticulum fragments.

• Proceedings of the Korean Biophysical Society Conference
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• 2003.06a
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• pp.19-19
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• 2003

We have developed a cardiac cell model (Kyoto Model) for the sinoatrial node and ventricle, which is composed of a common set of kinetic equations of membrane ionic currents, Ca$\^$2+/dynamics of sarcoplasmic reticulum and contractile protein. To expand this model by including metabolic pathways, the intracellular ATP metabolism, which is pivotal in cardiac excitation - contraction coupling, was incorporated. ATP consumption by the sarcolemmal Na$\^$+/ pump and the Ca pump in the sarcoplasmic reticulum were calculated with stoichiometry of 3Na:2K:1ATP and 2Ca:1ATP, respectively. ATP consumption by contraction was estimated according to experimental data. Dependence of contraction on ATP and inorganic phosphate was modeled, based on data of skinned cardiac fiber. in production by mitochondrial oxidative phosphorylation was modified from Korzeniewski '||'&'||' Zoladz (2001), and creatine kinase and adenylate kinase reactions were incorporated. ATP dependence of ATP-sensitive K channel and L type Ca channel were also included.