Ryuichi Tatsumi - Academia.edu (original) (raw)

Papers by Ryuichi Tatsumi

Experimental Cell Research, Sep 1, 2023

Animal Science Journal, Oct 1, 2003

Myofibrillar proteins of vertebrate skeletal muscles are insoluble in solutions of ionic strength... more Myofibrillar proteins of vertebrate skeletal muscles are insoluble in solutions of ionic strength that approximate physiological conditions. We established a method to solubilize more than 80% of chicken breast muscle myofibrillar proteins in water for the use of meat as a source of food protein. SDS-polyacrylamide gel electrophoretic patterns of water-soluble myofibrillar proteins demonstrated that all identified myofibrillar proteins except connectin/titin were soluble in water. A part of a-actinin was released from myofibrils by repeated washing with 2.5 mmol/L NaCl and 5 mmol/L L-histidine solution, and subsequent destruction of connectin/titin in washed myofibrils by ultrasonication resulted in solubilization of a large fraction of chicken breast muscle myofibrillar proteins in water. Myofibrillar proteins of chicken leg, pork loin, beef shoulder loin, and lamb were also solubilized in water using this procedure.

The International Journal of Biochemistry & Cell Biology, Sep 1, 2014

Regenerative mechanisms that regulate intramuscular motor innervation are thought to reside in th... more Regenerative mechanisms that regulate intramuscular motor innervation are thought to reside in the spatiotemporal expression of axon-guidance molecules. Our previous studies proposed a heretofore unexplored role of resident myogenic stem cell (satellite cell)-derived myoblasts as a key presenter of a secreted neural chemorepellent semaphorin 3A (Sema3A); hepatocyte growth factor (HGF) triggered its expression exclusively at the early-differentiation phase. In order to verify this concept, the present study was designed to clarify a paracrine source of HGF release. In vitro experiments demonstrated that activated anti-inflammatory macrophages (CD206-positive M2) produce HGF and thereby promote myoblast chemoattraction and Sema3A expression. Media from pro-inflammatory macrophage cultures (M1) did not show any significant effect. M2 also enhanced the expression of myoblast-differentiation markers in culture, and infiltrated predominantly at the early-differentiation phase (3-5 days post-injury); M2 were confirmed to produce HGF as monitored by in vivo/ex vivo immunocytochemistry of CD11b/CD206/HGF-positive cells and by HGF in situ hybridization of cardiotoxin- or crush-injured tibialis anterior muscle, respectively. These studies advance our understanding of the stage-specific activation of Sema3A expression signaling. Findings, therefore, encourage the idea that M2 contribute to spatiotemporal up-regulation of extracellular Sema3A concentrations by producing HGF that, in turn, stimulates a burst of Sema3A secretion by myoblasts that are recruited to site of injury. This model may ensure a coordinated delay in re-attachment of motoneuron terminals onto damaged fibers early in muscle regeneration, and thus synchronize the recovery of muscle-fiber integrity and the early resolution of inflammation after injury.

International Journal of Molecular Sciences, Apr 26, 2021

This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

Rheological properties of an emulsion-type sausage prepared from deer meat and pork fat were comp... more Rheological properties of an emulsion-type sausage prepared from deer meat and pork fat were compared with those of experimental pork sausages and of commercial sausages. Deer meat sausage showed a softer texture than the experimental pork sausage. Three-dimensional structure, one of the characteristic structures of emulsiontype sausages, was clearly observed even in deer meat sausages by scanning electron microscopy, although the structure of deer meat sausages was slightly coarser than that of the experimental pork sausages. However, rheological parameters of deer sausages obtained in the present study were in the range of normal values observed for sausages sold in the market. The characteristics in color of deer meat sausage were darker than those of the experimental pork sausages, so that the color of deer meat sausage was similar to that of typical dried sausage such as salami in the market. Therefore, the present results indicate that emulsion-type sausage using deer meat will be acceptable by consumers with no problem.

Journal of Food Biochemistry, Jun 1, 2007

We investigated the effect of high-pressure treatment on the properties of cytoplasmic 5′-nucleot... more We investigated the effect of high-pressure treatment on the properties of cytoplasmic 5′-nucleotidase (NT), which converts inosine monophosphate (IMP) into inosine. After pressure treatment at 400 MPa, the activity of purified IMP-NT remained at almost 100%, but the activity of partially purified adenosine monophosphate (AMP)-NT decreased to about 40%. These data suggest that there is a difference in the pressure stability between the enzymes. In situ fluorescence spectroscopy of IMP-NT under pressure showed that its pressure-induced denaturation was reversible. When the pressure was reduced from the highest pressure to ambient pressure, hysteresis was observed. This suggests that high pressure treatment may lead to a partial change in the affinity of the subunits for each other once they have dissociated. The activities of IMP-NT and AMP-NT extracted from pressure-treated muscles decreased remarkably between 250 and 450 MPa, but IMP-NT was more stable than AMP-NT.

Journal of Food Biochemistry, Jun 1, 2007

This study evaluated the effect of high pressure on rabbit skeletal muscle, specifically on the p... more This study evaluated the effect of high pressure on rabbit skeletal muscle, specifically on the production of inosinic acid (IMP), one of "umami" components, and on the activity of adenosine triphosphate (AMP) deaminase, which plays a role in the conversion of AMP to IMP. By increasing the pressure (0.1 to 300 MPa), nucleotide analysis showed that IMP content in muscle increased instantly with a concomitant decrease in ATP content. The IMP content of muscle at 300 MPa was approximately 15% higher than with lower pressures (0.1-200 MPa) when stored for 1 week at 4C after pressurization. These results suggested that the metabolism of nucleotides in muscle was not significantly impaired by pressure treatment. At 300 MPa, AMP deaminase maintained approximately 70% of the activity at 0.1 MPa. In contrast, the activity of purified AMP deaminase was completely lost at 200 MPa, and irreversible conformational changes were observed by in situ fluorescence spectroscopy. These results indicated that purified AMP deaminase was irreversibly denatured under pressure as high as 300-400 MPa.

Journal of Biological Chemistry, Mar 1, 2010

The apoB RNA-editing enzyme, catalytic polypeptide-like (APOBEC) family of proteins includes APOB... more The apoB RNA-editing enzyme, catalytic polypeptide-like (APOBEC) family of proteins includes APOBEC1, APOBEC3, and activation-induced deaminase, all of which are zincdependent cytidine deaminases active on polynucleotides and involved in RNA editing or DNA mutation. In contrast, the biochemical and physiological functions of APOBEC2, a musclespecific member of the family, are unknown, although it has been speculated, like APOBEC1, to be an RNA-editing enzyme. Here, we show that, although expressed widely in striated muscle (with levels peaking late during myoblast differentiation), APOBEC2 is preferentially associated with slow-twitch muscle, with its abundance being considerably greater in soleus compared with gastrocnemius muscle and, within soleus muscle, in slow as opposed to fast muscle fibers. Its abundance also decreases following muscle denervation. We further show that APOBEC2-deficient mice harbor a markedly increased ratio of slow to fast fibers in soleus muscle and exhibit an ϳ15-20% reduction in body mass from birth onwards, with elderly mutant animals revealing clear histological evidence of a mild myopathy. Thus, APOBEC2 is essential for normal muscle development and maintenance of fiber-type ratios; although its molecular function remains to be identified, biochemical analyses do not especially argue for any role in RNA editing.

FEBS Open Bio, Apr 27, 2016

Bioscience, Biotechnology, and Biochemistry, 1998

The FASEB Journal, Jan 3, 2018

Apobec2 is a member of the activation-induced deaminase/apolipoprotein B mRNA editing enzyme cata... more Apobec2 is a member of the activation-induced deaminase/apolipoprotein B mRNA editing enzyme catalytic polypeptide cytidine deaminase family expressed in differentiated skeletal and cardiac muscle. We previously reported that Apobec2 deficiency in mice leads to a shift in muscle fiber type, myopathy, and diminished muscle mass. However, the mechanisms of myopathy caused by Apobec2 deficiency and its physiologic functions are unclear. Here we show that, although Apobec2 localizes to the sarcomeric Z-lines in mouse tissue and cultured myotubes, the sarcomeric structure is not affected in Apobec2-deficient muscle. In contrast, electron microscopy reveals enlarged mitochondria and mitochondria engulfed by autophagic vacuoles, suggesting that Apobec2 deficiency causes mitochondrial defects leading to increased mitophagy in skeletal muscle. Indeed, Apobec2 deficiency results in increased reactive oxygen species generation and depolarized mitochondria, leading to mitophagy as a defensive response. Furthermore, the exercise capacity of Apobec2 2/2 mice is impaired, implying Apobec2 deficiency results in ongoing muscle dysfunction. The presence of rimmed vacuoles in myofibers from 10-mo-old mice suggests that the chronic muscle damage impairs normal autophagy. We conclude that Apobec2 deficiency causes mitochondrial defects that increase muscle mitophagy, leading to myopathy and atrophy. Our findings demonstrate that Apobec2 is required for mitochondrial homeostasis to maintain normal skeletal muscle function.

Animal Science Journal, Dec 17, 2012

Journal of Biochemistry, Feb 1, 1994

When myofibrils prepared from chicken leg muscle were treated with a solution containing 0.1 mM C... more When myofibrils prepared from chicken leg muscle were treated with a solution containing 0.1 mM CaCl2 and 30 micrograms/ml of leupeptin, alpha-connectin, which exists as a longitudinal thin filament in a sarcomere, was split into beta-connectin and a 1,200-kDa subfragment. The native subfragment was successfully purified without using any denaturant: It was extracted with 1 M KI solution from the Ca-treated myofibrils and purified by TSKgel G6000PW column chromatography. About 10 mg of the subfragment was yielded from 100 g of starting muscle. Using immunofluorescence microscopy and immunoelectron microscopy, we show here that polyclonal antibodies against the 1,200-kDa subfragment bind to the Z-disk and the epitope, which is about 0.34 micron apart from the Z-disk at a sarcomere length of 2.6 microns; the 1,200-kDa subfragment constitutes the proximal region of connectin filaments. Purified alpha-actinin decorated alpha-connectin and the 1,200-kDa subfragment on nitrocellulose blots of myofibrillar proteins separated by SDS-PAGE. Therefore, we conclude that connectin filaments are anchored to the Z-disk by the binding of the 1,200-kDa subfragment to alpha-actinin.

Journal of Muscle Research and Cell Motility, Mar 9, 2017

was observed in type 2A and 2X fibers (MyHC2A-and MyHC2X-positive fibers) than type 1 fibers (MyH... more was observed in type 2A and 2X fibers (MyHC2A-and MyHC2X-positive fibers) than type 1 fibers (MyHC1-positive fibers) in soleus muscles. These results suggest that the soleus contains more IMCL owing to the higher population of type 2A fibers, and the difference in lipid accumulation between the soleus and EDL could depend on fiber type composition.

Animal Science Journal, Apr 1, 2019

In the skeletal muscle of most animals, there are two major classifications of fiber type; namely... more In the skeletal muscle of most animals, there are two major classifications of fiber type; namely, type 1 and type 2 fibers. Type 2 fibers are further subdivided into type 2A, 2X, and 2B fibers (Schiaffino & Reggiani, 2011). Type 2A and 2X fibers have characteristics intermediate between those of type 1 and type 2B fibers. Although type 2X fibers are sometimes recognized as fast-twitch glycolytic fibers, type 2B fibers have an even stronger fast-twitch glycolytic phenotype (Rivero, Talmadge, & Edgerton, 1999). These fiber types are generally classified according to myosin heavy chain (MyHC) isoforms. In rodent skeletal muscles, four

Physiological Reports, Sep 1, 2018

Dietary apple polyphenols (AP) have been shown to exhibit beneficial effects on muscle endurance.... more Dietary apple polyphenols (AP) have been shown to exhibit beneficial effects on muscle endurance. Fast-to-slow change in the composition of myosin heavy chains was known as one of the molecular mechanisms. Here, we examined the effects of dietary AP on the capillaries and mitochondria in the rat skeletal muscle to elucidate the mechanisms underlying muscular endurance enhancement. Twenty-four Wistar male rats were divided into three groups, namely, the control group, 0.5% AP group, and 5% AP group (n = 8 in each group). After a feeding period of 4 weeks, rats were dissected, gastrocnemius muscles were removed, and the density of capillaries and levels of mitochondrial proteins were analyzed. Capillary density of the gastrocnemius increased to 17.8% in rats fed with 5% AP as compared to the control rats. No significant change was observed in the mitochondrial content and dynamics (fusion/ fission) of regulatory proteins. To investigate the mechanisms underlying the increase in the capillary density, positive (vascular endothelial cell growth factor, VEGF) and negative (thrombosponsin-1, TSP-1) factors of angiogenesis were analyzed. TSP-1 expression significantly decreased in rats fed with 0.5% AP and 5% AP by approximately 25% and 40%, respectively, as compared with the control rats. There were no significant differences in VEGF expression. Thus, dietary AP may increase the muscle capillary density by decreasing TSP-1 expression. We concluded that the increase in the capillary density and the fast-to-slow change in myosin heavy chains by AP feeding are the main causes for muscle endurance enhancement in Wistar rats.

Animal Science Journal, Apr 1, 2010

Satellite cells, resident myogenic stem cells found in postnatal skeletal muscle, are most abunda... more Satellite cells, resident myogenic stem cells found in postnatal skeletal muscle, are most abundant during early postnatal development and sharply decline in frequency thereafter to adult levels in mice and rats. Therefore, postnatal changes in satellite cell mitotic activities are important aspects for further understanding a muscle growth strategy. In large meat-production animals, however, the traditional in vivo proliferation assay may be less realistic because it requires intra-peritoneal (ip) injection of huge dosage of mutagenic nucleosides, 3 H-labeled thymidine or bromodeoxyuridine (BrdU), at each age-time of sacrifice. We report in the present pilot study using rats that in vivo proliferation activity of satellite cells can be evaluated by an in vitro BrdU-incorporation assay in early cultures. Briefly, satellite cells were prepared from upper hind-limb and back muscles and maintained for 24 h with imposing by BrdU addition for the last 2 h, followed by the regular immunocytochemistry for determining BrdU-incorporated cell percentage. This in vitro assay demonstrated a rapid decrease in proliferating satellite cell frequency to the adult level during about 3-month period after birth, and yielded a high correlation to the measurements by the in vivo BrdU ip-injection method during the postnatal period examined from day-2 to month-11. The in vitro proliferation assay may be further adaptable for large domestic animals by the combination with a muscle biopsy technique that enables age-interval sampling from the same growing animals.

The International Journal of Biochemistry & Cell Biology, Apr 1, 2017

Recently we found that the deficiency of APOBEC2, a member of apoB mRNA editing enzyme, catalytic... more Recently we found that the deficiency of APOBEC2, a member of apoB mRNA editing enzyme, catalytic polypeptide-like family, leads to a diminished muscle mass and increased myofiber with centrally-located nuclei known as dystrophic phenotypes. APOBEC2 expression is predominant in skeletal and cardiac muscles and elevated exclusively at the early-differentiation phase of wild-type (WT) myoblast cultures; however the physiological significance is still unknown. Here we show that APOBEC2 is a key negative regulator of myoblast differentiation in muscle regeneration. APOBEC2-knockout (A2KO) mice myoblast cultures displayed a normal morphology of primary myotubes along with earlier increase in fusion index and higher expression levels of myosin heavy chain (MyHC), myogenin and its cooperating factor MEF2C than WT myoblasts. Similar response was observable in APOBEC2-knockdown cultures of WT myoblasts that were transfected with the specific siRNA at the differentiation phase (not proliferation phase). Importantly, cardiotoxin-injured A2KO gastrocnemius muscle provided in vivo evidence by showing larger up-regulation of neonatal MyHC and myogenin and hence earlier regeneration of myofiber structures with diminished cross-sectional areas and minimal Feret diameters. Therefore, the findings highlight a promising role for APOBEC2 in normal progression of regenerative myogenesis at the early-differentiation phase upon muscle injury.

Experimental Cell Research, Sep 1, 2023

Animal Science Journal, Oct 1, 2003

Myofibrillar proteins of vertebrate skeletal muscles are insoluble in solutions of ionic strength... more Myofibrillar proteins of vertebrate skeletal muscles are insoluble in solutions of ionic strength that approximate physiological conditions. We established a method to solubilize more than 80% of chicken breast muscle myofibrillar proteins in water for the use of meat as a source of food protein. SDS-polyacrylamide gel electrophoretic patterns of water-soluble myofibrillar proteins demonstrated that all identified myofibrillar proteins except connectin/titin were soluble in water. A part of a-actinin was released from myofibrils by repeated washing with 2.5 mmol/L NaCl and 5 mmol/L L-histidine solution, and subsequent destruction of connectin/titin in washed myofibrils by ultrasonication resulted in solubilization of a large fraction of chicken breast muscle myofibrillar proteins in water. Myofibrillar proteins of chicken leg, pork loin, beef shoulder loin, and lamb were also solubilized in water using this procedure.

The International Journal of Biochemistry & Cell Biology, Sep 1, 2014

Regenerative mechanisms that regulate intramuscular motor innervation are thought to reside in th... more Regenerative mechanisms that regulate intramuscular motor innervation are thought to reside in the spatiotemporal expression of axon-guidance molecules. Our previous studies proposed a heretofore unexplored role of resident myogenic stem cell (satellite cell)-derived myoblasts as a key presenter of a secreted neural chemorepellent semaphorin 3A (Sema3A); hepatocyte growth factor (HGF) triggered its expression exclusively at the early-differentiation phase. In order to verify this concept, the present study was designed to clarify a paracrine source of HGF release. In vitro experiments demonstrated that activated anti-inflammatory macrophages (CD206-positive M2) produce HGF and thereby promote myoblast chemoattraction and Sema3A expression. Media from pro-inflammatory macrophage cultures (M1) did not show any significant effect. M2 also enhanced the expression of myoblast-differentiation markers in culture, and infiltrated predominantly at the early-differentiation phase (3-5 days post-injury); M2 were confirmed to produce HGF as monitored by in vivo/ex vivo immunocytochemistry of CD11b/CD206/HGF-positive cells and by HGF in situ hybridization of cardiotoxin- or crush-injured tibialis anterior muscle, respectively. These studies advance our understanding of the stage-specific activation of Sema3A expression signaling. Findings, therefore, encourage the idea that M2 contribute to spatiotemporal up-regulation of extracellular Sema3A concentrations by producing HGF that, in turn, stimulates a burst of Sema3A secretion by myoblasts that are recruited to site of injury. This model may ensure a coordinated delay in re-attachment of motoneuron terminals onto damaged fibers early in muscle regeneration, and thus synchronize the recovery of muscle-fiber integrity and the early resolution of inflammation after injury.

International Journal of Molecular Sciences, Apr 26, 2021

This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

Rheological properties of an emulsion-type sausage prepared from deer meat and pork fat were comp... more Rheological properties of an emulsion-type sausage prepared from deer meat and pork fat were compared with those of experimental pork sausages and of commercial sausages. Deer meat sausage showed a softer texture than the experimental pork sausage. Three-dimensional structure, one of the characteristic structures of emulsiontype sausages, was clearly observed even in deer meat sausages by scanning electron microscopy, although the structure of deer meat sausages was slightly coarser than that of the experimental pork sausages. However, rheological parameters of deer sausages obtained in the present study were in the range of normal values observed for sausages sold in the market. The characteristics in color of deer meat sausage were darker than those of the experimental pork sausages, so that the color of deer meat sausage was similar to that of typical dried sausage such as salami in the market. Therefore, the present results indicate that emulsion-type sausage using deer meat will be acceptable by consumers with no problem.

Journal of Food Biochemistry, Jun 1, 2007

We investigated the effect of high-pressure treatment on the properties of cytoplasmic 5′-nucleot... more We investigated the effect of high-pressure treatment on the properties of cytoplasmic 5′-nucleotidase (NT), which converts inosine monophosphate (IMP) into inosine. After pressure treatment at 400 MPa, the activity of purified IMP-NT remained at almost 100%, but the activity of partially purified adenosine monophosphate (AMP)-NT decreased to about 40%. These data suggest that there is a difference in the pressure stability between the enzymes. In situ fluorescence spectroscopy of IMP-NT under pressure showed that its pressure-induced denaturation was reversible. When the pressure was reduced from the highest pressure to ambient pressure, hysteresis was observed. This suggests that high pressure treatment may lead to a partial change in the affinity of the subunits for each other once they have dissociated. The activities of IMP-NT and AMP-NT extracted from pressure-treated muscles decreased remarkably between 250 and 450 MPa, but IMP-NT was more stable than AMP-NT.

Journal of Food Biochemistry, Jun 1, 2007

This study evaluated the effect of high pressure on rabbit skeletal muscle, specifically on the p... more This study evaluated the effect of high pressure on rabbit skeletal muscle, specifically on the production of inosinic acid (IMP), one of "umami" components, and on the activity of adenosine triphosphate (AMP) deaminase, which plays a role in the conversion of AMP to IMP. By increasing the pressure (0.1 to 300 MPa), nucleotide analysis showed that IMP content in muscle increased instantly with a concomitant decrease in ATP content. The IMP content of muscle at 300 MPa was approximately 15% higher than with lower pressures (0.1-200 MPa) when stored for 1 week at 4C after pressurization. These results suggested that the metabolism of nucleotides in muscle was not significantly impaired by pressure treatment. At 300 MPa, AMP deaminase maintained approximately 70% of the activity at 0.1 MPa. In contrast, the activity of purified AMP deaminase was completely lost at 200 MPa, and irreversible conformational changes were observed by in situ fluorescence spectroscopy. These results indicated that purified AMP deaminase was irreversibly denatured under pressure as high as 300-400 MPa.

Journal of Biological Chemistry, Mar 1, 2010

The apoB RNA-editing enzyme, catalytic polypeptide-like (APOBEC) family of proteins includes APOB... more The apoB RNA-editing enzyme, catalytic polypeptide-like (APOBEC) family of proteins includes APOBEC1, APOBEC3, and activation-induced deaminase, all of which are zincdependent cytidine deaminases active on polynucleotides and involved in RNA editing or DNA mutation. In contrast, the biochemical and physiological functions of APOBEC2, a musclespecific member of the family, are unknown, although it has been speculated, like APOBEC1, to be an RNA-editing enzyme. Here, we show that, although expressed widely in striated muscle (with levels peaking late during myoblast differentiation), APOBEC2 is preferentially associated with slow-twitch muscle, with its abundance being considerably greater in soleus compared with gastrocnemius muscle and, within soleus muscle, in slow as opposed to fast muscle fibers. Its abundance also decreases following muscle denervation. We further show that APOBEC2-deficient mice harbor a markedly increased ratio of slow to fast fibers in soleus muscle and exhibit an ϳ15-20% reduction in body mass from birth onwards, with elderly mutant animals revealing clear histological evidence of a mild myopathy. Thus, APOBEC2 is essential for normal muscle development and maintenance of fiber-type ratios; although its molecular function remains to be identified, biochemical analyses do not especially argue for any role in RNA editing.

FEBS Open Bio, Apr 27, 2016

Bioscience, Biotechnology, and Biochemistry, 1998

The FASEB Journal, Jan 3, 2018

Apobec2 is a member of the activation-induced deaminase/apolipoprotein B mRNA editing enzyme cata... more Apobec2 is a member of the activation-induced deaminase/apolipoprotein B mRNA editing enzyme catalytic polypeptide cytidine deaminase family expressed in differentiated skeletal and cardiac muscle. We previously reported that Apobec2 deficiency in mice leads to a shift in muscle fiber type, myopathy, and diminished muscle mass. However, the mechanisms of myopathy caused by Apobec2 deficiency and its physiologic functions are unclear. Here we show that, although Apobec2 localizes to the sarcomeric Z-lines in mouse tissue and cultured myotubes, the sarcomeric structure is not affected in Apobec2-deficient muscle. In contrast, electron microscopy reveals enlarged mitochondria and mitochondria engulfed by autophagic vacuoles, suggesting that Apobec2 deficiency causes mitochondrial defects leading to increased mitophagy in skeletal muscle. Indeed, Apobec2 deficiency results in increased reactive oxygen species generation and depolarized mitochondria, leading to mitophagy as a defensive response. Furthermore, the exercise capacity of Apobec2 2/2 mice is impaired, implying Apobec2 deficiency results in ongoing muscle dysfunction. The presence of rimmed vacuoles in myofibers from 10-mo-old mice suggests that the chronic muscle damage impairs normal autophagy. We conclude that Apobec2 deficiency causes mitochondrial defects that increase muscle mitophagy, leading to myopathy and atrophy. Our findings demonstrate that Apobec2 is required for mitochondrial homeostasis to maintain normal skeletal muscle function.

Animal Science Journal, Dec 17, 2012

Journal of Biochemistry, Feb 1, 1994

When myofibrils prepared from chicken leg muscle were treated with a solution containing 0.1 mM C... more When myofibrils prepared from chicken leg muscle were treated with a solution containing 0.1 mM CaCl2 and 30 micrograms/ml of leupeptin, alpha-connectin, which exists as a longitudinal thin filament in a sarcomere, was split into beta-connectin and a 1,200-kDa subfragment. The native subfragment was successfully purified without using any denaturant: It was extracted with 1 M KI solution from the Ca-treated myofibrils and purified by TSKgel G6000PW column chromatography. About 10 mg of the subfragment was yielded from 100 g of starting muscle. Using immunofluorescence microscopy and immunoelectron microscopy, we show here that polyclonal antibodies against the 1,200-kDa subfragment bind to the Z-disk and the epitope, which is about 0.34 micron apart from the Z-disk at a sarcomere length of 2.6 microns; the 1,200-kDa subfragment constitutes the proximal region of connectin filaments. Purified alpha-actinin decorated alpha-connectin and the 1,200-kDa subfragment on nitrocellulose blots of myofibrillar proteins separated by SDS-PAGE. Therefore, we conclude that connectin filaments are anchored to the Z-disk by the binding of the 1,200-kDa subfragment to alpha-actinin.

Journal of Muscle Research and Cell Motility, Mar 9, 2017

was observed in type 2A and 2X fibers (MyHC2A-and MyHC2X-positive fibers) than type 1 fibers (MyH... more was observed in type 2A and 2X fibers (MyHC2A-and MyHC2X-positive fibers) than type 1 fibers (MyHC1-positive fibers) in soleus muscles. These results suggest that the soleus contains more IMCL owing to the higher population of type 2A fibers, and the difference in lipid accumulation between the soleus and EDL could depend on fiber type composition.

Animal Science Journal, Apr 1, 2019

In the skeletal muscle of most animals, there are two major classifications of fiber type; namely... more In the skeletal muscle of most animals, there are two major classifications of fiber type; namely, type 1 and type 2 fibers. Type 2 fibers are further subdivided into type 2A, 2X, and 2B fibers (Schiaffino & Reggiani, 2011). Type 2A and 2X fibers have characteristics intermediate between those of type 1 and type 2B fibers. Although type 2X fibers are sometimes recognized as fast-twitch glycolytic fibers, type 2B fibers have an even stronger fast-twitch glycolytic phenotype (Rivero, Talmadge, & Edgerton, 1999). These fiber types are generally classified according to myosin heavy chain (MyHC) isoforms. In rodent skeletal muscles, four

Physiological Reports, Sep 1, 2018

Dietary apple polyphenols (AP) have been shown to exhibit beneficial effects on muscle endurance.... more Dietary apple polyphenols (AP) have been shown to exhibit beneficial effects on muscle endurance. Fast-to-slow change in the composition of myosin heavy chains was known as one of the molecular mechanisms. Here, we examined the effects of dietary AP on the capillaries and mitochondria in the rat skeletal muscle to elucidate the mechanisms underlying muscular endurance enhancement. Twenty-four Wistar male rats were divided into three groups, namely, the control group, 0.5% AP group, and 5% AP group (n = 8 in each group). After a feeding period of 4 weeks, rats were dissected, gastrocnemius muscles were removed, and the density of capillaries and levels of mitochondrial proteins were analyzed. Capillary density of the gastrocnemius increased to 17.8% in rats fed with 5% AP as compared to the control rats. No significant change was observed in the mitochondrial content and dynamics (fusion/ fission) of regulatory proteins. To investigate the mechanisms underlying the increase in the capillary density, positive (vascular endothelial cell growth factor, VEGF) and negative (thrombosponsin-1, TSP-1) factors of angiogenesis were analyzed. TSP-1 expression significantly decreased in rats fed with 0.5% AP and 5% AP by approximately 25% and 40%, respectively, as compared with the control rats. There were no significant differences in VEGF expression. Thus, dietary AP may increase the muscle capillary density by decreasing TSP-1 expression. We concluded that the increase in the capillary density and the fast-to-slow change in myosin heavy chains by AP feeding are the main causes for muscle endurance enhancement in Wistar rats.

Animal Science Journal, Apr 1, 2010

Satellite cells, resident myogenic stem cells found in postnatal skeletal muscle, are most abunda... more Satellite cells, resident myogenic stem cells found in postnatal skeletal muscle, are most abundant during early postnatal development and sharply decline in frequency thereafter to adult levels in mice and rats. Therefore, postnatal changes in satellite cell mitotic activities are important aspects for further understanding a muscle growth strategy. In large meat-production animals, however, the traditional in vivo proliferation assay may be less realistic because it requires intra-peritoneal (ip) injection of huge dosage of mutagenic nucleosides, 3 H-labeled thymidine or bromodeoxyuridine (BrdU), at each age-time of sacrifice. We report in the present pilot study using rats that in vivo proliferation activity of satellite cells can be evaluated by an in vitro BrdU-incorporation assay in early cultures. Briefly, satellite cells were prepared from upper hind-limb and back muscles and maintained for 24 h with imposing by BrdU addition for the last 2 h, followed by the regular immunocytochemistry for determining BrdU-incorporated cell percentage. This in vitro assay demonstrated a rapid decrease in proliferating satellite cell frequency to the adult level during about 3-month period after birth, and yielded a high correlation to the measurements by the in vivo BrdU ip-injection method during the postnatal period examined from day-2 to month-11. The in vitro proliferation assay may be further adaptable for large domestic animals by the combination with a muscle biopsy technique that enables age-interval sampling from the same growing animals.

The International Journal of Biochemistry & Cell Biology, Apr 1, 2017

Recently we found that the deficiency of APOBEC2, a member of apoB mRNA editing enzyme, catalytic... more Recently we found that the deficiency of APOBEC2, a member of apoB mRNA editing enzyme, catalytic polypeptide-like family, leads to a diminished muscle mass and increased myofiber with centrally-located nuclei known as dystrophic phenotypes. APOBEC2 expression is predominant in skeletal and cardiac muscles and elevated exclusively at the early-differentiation phase of wild-type (WT) myoblast cultures; however the physiological significance is still unknown. Here we show that APOBEC2 is a key negative regulator of myoblast differentiation in muscle regeneration. APOBEC2-knockout (A2KO) mice myoblast cultures displayed a normal morphology of primary myotubes along with earlier increase in fusion index and higher expression levels of myosin heavy chain (MyHC), myogenin and its cooperating factor MEF2C than WT myoblasts. Similar response was observable in APOBEC2-knockdown cultures of WT myoblasts that were transfected with the specific siRNA at the differentiation phase (not proliferation phase). Importantly, cardiotoxin-injured A2KO gastrocnemius muscle provided in vivo evidence by showing larger up-regulation of neonatal MyHC and myogenin and hence earlier regeneration of myofiber structures with diminished cross-sectional areas and minimal Feret diameters. Therefore, the findings highlight a promising role for APOBEC2 in normal progression of regenerative myogenesis at the early-differentiation phase upon muscle injury.