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Biomedicine / [publiee Pour... Mar 19751) The contractile system consists of thick and thin filaments arranged side by side in a double network of hexagonal cross-section. 2) The thick filaments are... (Review)
Review
1) The contractile system consists of thick and thin filaments arranged side by side in a double network of hexagonal cross-section. 2) The thick filaments are principally made up of myosin and the thin ones of actin, tropomyosin and troponin. 3) Myosin is an enzyme catalysing the hydrolysis of ATP; actin increases the specific activity of this enzyme, converting it from a Ca+2 sensitive ATPase to a Mg+2 sensitive ATPase. 4) Hydrolysis of the last phosphoryl group of adenosine triphosphate (ATP) salts is the energy source for muscle contraction. 5) The adenosine diphosphate (ADP) salts, formed by ATP splitting, are rephosphorylated and reinjected into the myofibril.
Topics: Actins; Adenosine Triphosphate; Animals; Creatine; Energy Metabolism; Models, Anatomic; Muscle Contraction; Muscles; Myofibrils; Myosins; Tropomyosin; Troponin
PubMed: 764891
DOI: No ID Found -
Journal of Ethnopharmacology Apr 2022Glabridin, extracted from Glycyrrhiza glabra L., is widely used for the treatment of hyperpigmentation because of its anti-inflammatory and antioxidant activities and...
ETHNOPHARMACOLOGICAL RELEVANCE
Glabridin, extracted from Glycyrrhiza glabra L., is widely used for the treatment of hyperpigmentation because of its anti-inflammatory and antioxidant activities and its ability to inhibit melanin synthesis. This led to the strict regulation of its quality and safety. However, traditional quality control methods used for plant extracts cannot reflect the product quality owing to multiple unknown impurities, which necessitates the further analysis of impurities.
AIM OF THE STUDY
The study identified the toxic impurities of glabridin and their toxicological mechanism.
MATERIALS AND METHODS
In total, 10 glabridin samples from different sources were quantified using high-performance liquid chromatography. Sample toxicities were evaluated using zebrafish and cell models. To identify impurities, samples with different toxicity were analyzed by ultra-high-performance liquid chromatography coupled with quadrupole-Orbitrap mass spectrometry. The toxicity of related impurities was verified in the zebrafish model. Phalloidin stain was used to evaluate subtle changes in myofibril alignment.
RESULTS
Although glabridin content in the samples was similar, there were significant differences in toxicity. The results were verified using four different mammalian cell lines. Higher contents of glabrone and glabrol were identified in the sample with the highest toxicity. In the zebrafish model, the addition of glabrol reduced the LC of glabridin to 9.224, 6.229, and 5.370 μM at 48, 72, and 96 h post-fertilization, respectively, whereas glabrone did not have any toxic effect. Phalloidin staining indicated that a glabrol impurity exacerbates the myotoxicity of glabridin in zebrafish embryos.
CONCLUSION
Glabrol, but not glabrone, was identified as a key impurity that increased glabridin toxicity. This finding indicates that controlling glabrol content is necessary during glabridin product production.
Topics: Animals; Cell Line; Cell Line, Tumor; Chromatography, High Pressure Liquid; Embryo, Nonmammalian; Female; Flavonoids; Glycyrrhiza; Humans; Isoflavones; Male; Mass Spectrometry; Mice; Myofibrils; Phenols; Plant Extracts; Quality Control; Zebrafish
PubMed: 34971733
DOI: 10.1016/j.jep.2021.114963 -
Meat Science Apr 2023The effect of pre-rigor temperature incubation on the activity and distribution in sarcoplasmic and myofibrillar fractions of calpains, and meat quality attributes was...
The effect of pre-rigor temperature incubation on the activity and distribution in sarcoplasmic and myofibrillar fractions of calpains, and meat quality attributes was investigated. Porcine longissimus thoracis muscles were incubated pre-rigor at 14, 22, 30 and 38 °C to 6 h postmortem, followed by another 2 h incubation at 14 °C. Thereafter, muscles were stored at 2 °C for 1 or 4 days. With higher pre-rigor temperature, sarcoplasmic Ca concentration, purge loss and myofibril-bound calpain-1 content increased, while shear force declined. Water-holding capacity of isolated myofibrils was lower after pre-rigor incubation at 38 °C. Desmin and troponin T degradation, and myofibril fragmentation was greater upon incubation of isolated myofibrils with added Ca in the order 800 μM Ca > 40 μM Ca > no Ca, suggesting that calpain-1 and calpain-2 were associated to myofibrils and proteolytically active with sufficient Ca. Activity of myofibril-bound calpain-1 in muscle incubated pre-rigor at 22 and 30 °C were higher than when incubated at 14 and 38 °C. These results indicate that calpains translocate from the sarcoplasm onto myofibrils with higher pre-rigor temperature to 30 °C and the proteolytic potential of myofibril-associated calpains is thereby increased.
Topics: Swine; Animals; Proteolysis; Myofibrils; Calpain; Red Meat; Pork Meat; Temperature; Muscle, Skeletal; Meat
PubMed: 36608417
DOI: 10.1016/j.meatsci.2022.109094 -
Cellular Signalling Aug 2016The mechanotransduction signaling pathways initiated in heart muscle by increased mechanical loading are known to lead to long-term transcriptional changes and...
The mechanotransduction signaling pathways initiated in heart muscle by increased mechanical loading are known to lead to long-term transcriptional changes and hypertrophy, but the rapid events for adaptation at the sarcomeric level are not fully understood. The goal of this study was to test the hypothesis that actin filament assembly during cardiomyocyte growth is regulated by post-translational modifications (PTMs) of CapZβ1. In rapidly hypertrophying neonatal rat ventricular myocytes (NRVMs) stimulated by phenylephrine (PE), two-dimensional gel electrophoresis (2DGE) of CapZβ1 revealed a shift toward more negative charge. Consistent with this, mass spectrometry identified CapZβ1 phosphorylation on serine-204 and acetylation on lysine-199, two residues which are near the actin binding surface of CapZβ1. Ectopic expression of dominant negative PKCɛ (dnPKCɛ) in NRVMs blunted the PE-induced increase in CapZ dynamics, as evidenced by the kinetic constant (Kfrap) of fluorescence recovery after photobleaching (FRAP), and concomitantly reduced phosphorylation and acetylation of CapZβ1. Furthermore, inhibition of class I histone deacetylases (HDACs) increased lysine-199 acetylation on CapZβ1, which increased Kfrap of CapZ and stimulated actin dynamics. Finally, we show that PE treatment of NRVMs results in decreased binding of HDAC3 to myofibrils, suggesting a signal-dependent mechanism for the regulation of sarcomere-associated CapZβ1 acetylation. Taken together, this dual regulation through phosphorylation and acetylation of CapZβ1 provides a novel model for the regulation of myofibril growth during cardiac hypertrophy.
Topics: Acetylation; Actins; Amino Acid Sequence; Animals; Animals, Newborn; CapZ Actin Capping Protein; Cardiomegaly; Cell Size; Heart Ventricles; Histone Deacetylase Inhibitors; Histone Deacetylases; Models, Biological; Myocytes, Cardiac; Myofibrils; Phenylephrine; Phosphorylation; Protein Kinase C-epsilon; Protein Processing, Post-Translational; Rats, Sprague-Dawley; Sarcomeres
PubMed: 27185186
DOI: 10.1016/j.cellsig.2016.05.011 -
Cytoskeleton (Hoboken, N.J.) Oct 2021Details of sarcomeric protein assembly during de novo myofibril formation closely resemble myofibrillogenesis in skeletal and cardiac myocytes in birds, rodents, and...
Details of sarcomeric protein assembly during de novo myofibril formation closely resemble myofibrillogenesis in skeletal and cardiac myocytes in birds, rodents, and zebrafish. The arrangement of proteins during myofibrillogenesis follows a three-step process: beginning with premyofibrils, followed by nascent myofibrils, and concluding with mature myofibrils (reviewed in Sanger et al., 2017). Assembly and maintenance of myofibrils in living muscle cells. In: Handbook of experimental pharmacology, 2017 [pp. 39-75]. Our aim is to determine if the same pathway is followed in human cardiomyocytes derived from human inducible pluripotent stem cells. We found that the human cardiomyocytes developed patterns of protein organization identical to the three-step series seen in the model organisms cited above. Further experiments showed that myofibril assembly can be blocked at the nascent myofibril by five different inhibitors of the Ubiquitin Proteasome System (UPS) stage in both avian and human cardiomyocytes. With the exception of Carfilzomib, removal of the UPS inhibitors allows nascent myofibrils to proceed to mature myofibrils. Some proteasomal inhibitors, such as Bortezomib and Carfilzomib, used to treat multiple myeloma patients, have off-target effects of damage to hearts in three to 6 % of these patients. These cardiovascular adverse events may result from prevention of mature myofibril formation in the cardiomyocytes. In summary, our results support a common three-step model for the formation of myofibrils ranging from avian to human cardiomyocytes. The Ubiquitin Proteasome System is required for progression from nascent myofibrils to mature myofibrils. Our experiments suggest a possible explanation for the cardiac and skeletal muscle off-target effects reported in multiple myeloma patients treated with proteasome inhibitors.
Topics: Animals; Cells, Cultured; Chick Embryo; Humans; Multiple Myeloma; Myocytes, Cardiac; Myofibrils; Pluripotent Stem Cells; Proteasome Endopeptidase Complex; Ubiquitin; Zebrafish
PubMed: 35502133
DOI: 10.1002/cm.21697 -
The American Journal of Physiology Feb 1987A novel instrument for measuring the mechanics of a single myofibril is described. The principle of the transducer operation is to attach a myofibril to a very fine wire...
A novel instrument for measuring the mechanics of a single myofibril is described. The principle of the transducer operation is to attach a myofibril to a very fine wire suspended in a magnetic field. Feedback circuits pass current through the wire to maintain the length constant when the myofibril contracts. The wire position is measured optoelectronically at a resolution below 1 A. The myofibril measurement system consists of two independent transducers and is capable of resolving tension down to 0.5 ng/square root Hz and controlling the myofibril length with a 10-microseconds rise time. Optical and electronic designs of the system and calibration and adjustment procedures are described. Experimental chamber design, a flow controller, and an environmental noise cancellation scheme are also discussed.
Topics: Biomechanical Phenomena; Calibration; Magnetics; Muscle Contraction; Myofibrils; Optics and Photonics; Sarcomeres; Solutions; Specimen Handling; Transducers
PubMed: 3826338
DOI: 10.1152/ajpcell.1987.252.2.C253 -
The Journal of Cell Biology Oct 2018Myofibril breakdown is a fundamental cause of muscle wasting and inevitable sequel of aging and disease. We demonstrated that myofibril loss requires depolymerization of...
Myofibril breakdown is a fundamental cause of muscle wasting and inevitable sequel of aging and disease. We demonstrated that myofibril loss requires depolymerization of the desmin cytoskeleton, which is activated by phosphorylation. Here, we developed a mass spectrometry-based kinase-trap assay and identified glycogen synthase kinase 3-β (GSK3-β) as responsible for desmin phosphorylation. GSK3-β inhibition in mice prevented desmin phosphorylation and depolymerization and blocked atrophy upon fasting or denervation. Desmin was phosphorylated by GSK3-β 3 d after denervation, but depolymerized only 4 d later when cytosolic Ca levels rose. Mass spectrometry analysis identified GSK3-β and the Ca-specific protease, calpain-1, bound to desmin and catalyzing its disassembly. Consistently, calpain-1 down-regulation prevented loss of phosphorylated desmin and blocked atrophy. Thus, phosphorylation of desmin filaments by GSK3-β is a key molecular event required for calpain-1-mediated depolymerization, and the subsequent myofibril destruction. Consequently, GSK3-β represents a novel drug target to prevent myofibril breakdown and atrophy.
Topics: Animals; Calcium; Calpain; Desmin; Down-Regulation; Gene Expression Regulation, Developmental; Glycogen Synthase Kinase 3 beta; Male; Mice; Muscular Atrophy; Myofibrils; Phosphorylation
PubMed: 30061109
DOI: 10.1083/jcb.201802018 -
Animal Science Journal = Nihon Chikusan... Jul 2019Skeletal muscle consists of bundles of myofibers containing millions of myofibrils, each of which is formed of longitudinally aligned sarcomere structures. Sarcomeres... (Review)
Review
Skeletal muscle consists of bundles of myofibers containing millions of myofibrils, each of which is formed of longitudinally aligned sarcomere structures. Sarcomeres are the minimum contractile unit, which mainly consists of four components: Z-bands, thin filaments, thick filaments, and connectin/titin. The size and shape of the sarcomere component is strictly controlled. Surprisingly, skeletal muscle cells not only synthesize a series of myofibrillar proteins but also regulate the assembly of those proteins into the sarcomere structures. However, authentic sarcomere structures cannot be reconstituted by combining purified myofibrillar proteins in vitro, therefore there must be an elaborate mechanism ensuring the correct formation of myofibril structure in skeletal muscle cells. This review discusses the role of myosin, a main component of the thick filament, in thick filament formation and the dynamics of myosin in skeletal muscle cells. Changes in the number of myofibrils in myofibers can cause muscle hypertrophy or atrophy. Therefore, it is important to understand the fundamental mechanisms by which myofibers control myofibril formation at the molecular level to develop approaches that effectively enhance muscle growth in animals.
Topics: Animals; Atrophy; Cytoskeleton; Hypertrophy; Muscle, Skeletal; Myofibrils; Myosins; Sarcomeres
PubMed: 31134719
DOI: 10.1111/asj.13226 -
Journal of Food Science Aug 2018Bromelain was used to tenderize golden pomfrets (Trachinotus blochii). The enzyme kinetic model was x=2.447×ln[1+(1332.21×E0S0-1.74)t], which indicated that the degree...
UNLABELLED
Bromelain was used to tenderize golden pomfrets (Trachinotus blochii). The enzyme kinetic model was x=2.447×ln[1+(1332.21×E0S0-1.74)t], which indicated that the degree of hydrolysis (DH, x) was dependent on hydrolysis time (t), the initial concentration of myofibril (S ) and bromelain (E ). The relationship between the overall hydrolysis rate (v), S , E , and t is demonstrated as: v=(16.50(E0S0)-1.33)S0 exp {-2.447ln[1+(1332.21E0S0-1.74)t2]}. Sample of 0.40% E /S was further used to study the effects of hydrolysis time on the changes of proteins, peptides, free amino acids (FAA), and protein nanostructure. SDS-PAGE result showed that myosin heavy chain was degraded dramatically from 22.88% before treatment to 12.03% after 2 min bromelain treatment. Meanwhile, bromelain did not exhibit activity towards actin, trypomyosin, myosin light chain, and troponin C. A general increase of amino acids indicated the increased DH and the preferential cleavage sites of bromelain in the descending order of lysine, glutamic acid, glycine, ornithine, methionine sulfoxide, and alanine. Atomic force microscope images showed that the strip-like structure of myofibril was considerably degraded by bromelain, and the granulation of protein after 20 min indicated possible self-assembling of protein hydrolysate. Confocal laser scanning microscopy further confirmed the degradation of myofibril proteins and formation of protein aggregates.
PRACTICAL APPLICATION
Meat of golden pomfrets is tough, thus not idea for fish balls or fish cakes. Tenderization is essential to achieve desired texture and consumer acceptance, especially for this fish meat with intrinsic hard texture. Bromelain can be extracted from pineapple processing waste. Enzymatic kinetics was studied to instruct industry to control the tenderness of the processed fish meat. The microstructural and mechanism study elucidate the process, thus could be applied to improve the quality of the seafood products correspondingly.
Topics: Amino Acids; Ananas; Animals; Bromelains; Fishes; Food Handling; Hydrolysis; Kinetics; Meat; Myofibrils; Protein Hydrolysates; Proteins; Seafood
PubMed: 30020543
DOI: 10.1111/1750-3841.14212 -
Trends in Genetics : TIG Apr 1990Myofibrils, the contractile organelles of muscle, are apt subjects for studies on the formation and function of actomyosin networks. Molecular genetic approaches are... (Review)
Review
Myofibrils, the contractile organelles of muscle, are apt subjects for studies on the formation and function of actomyosin networks. Molecular genetic approaches are advancing our understanding of myofibril structure and assembly, and may offer a novel and useful approach for investigating the crossbridge cycle. We review recent progress in Drosophila.
Topics: Animals; Drosophila melanogaster; Exons; Muscle Contraction; Muscle Proteins; Mutation; Myofibrils; Myosins
PubMed: 2132732
DOI: 10.1016/0168-9525(90)90127-r