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Copyright of Aquatic Animals Nutrition is the property of University of Guilan, Department of Fisheries, Faculty of Natural Resources and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Yellowfin tuna (Thunnus albacares) is the world's second-largest commodity with good nutrition. After processing, some wastes / residues / by-products can be used to produce surimi which still retains the tuna meat properties. The manufacturing of surimi requires safe preservatives, such as the natural preservative, atung (Parinarium glaberimum Hassk), which contains antibacterial substances. Therefore, the present work aimed to determine the effectiveness of 4% (w/v) atung solution on the quantity and quality of yellowfin tuna surimi produced from tuna by-products. The fish meat was treated with a washing agent of ice water and 4% atung solution with several washing frequencies. The parameters assessed were the yield and quality of surimi by analysing the protein content, myofibrillar protein content (salt soluble), water-holding capacity, Salmonella spp., and E. coli. In addition, the parameters included teeth-cutting, ashi strength, and folding. The 4% (w/v) atung solution effectively produced tuna fish surimi with 68.50% yield, 20.62% protein, 8.87% myofibrillar protein, and free from Salmonella spp. and E. coli. The waterholding capacity of the surimi was recorded at 68.9% and increased to 73.3% after three washes. The use of 4% (b/v) atung solution effectively produced surimi with a teethcutting value of 7.80 - 7.92, and an ashi strength of 7.97 - 8.08, whereas the folding test was B to A (3.80) after four washes. [ABSTRACT FROM AUTHOR]

The present study was carried out to find the muscle protein fractionation (myofibrillar, sarcoplasmic, and stromal proteins) and found that the fresh broiler meat samples had a myofibrillar, sarcoplasmic, and stromal protein content (%) of 11.46, 5.80, and 1.53%, respectively. The overall mean myofibrillar, sarcoplasmic, and stromal protein content (%) of frozen meat samples at 1st month were 10.47, 5.77, and 1.71 and 12th month were 10.45, 5.80, and 1.68 exhibited significant difference (P < 0.01) individually among them. The myofibrillar, sarcoplasmic, and stromal protein contents (percent) of the frozen samples stored at -12°C were 10.50, 5.88, and 1.66 and samples stored at -18°C were 10.56, 5.72, and 1.71 and samples stored at -24°C were 10.58, 5.84, and 1.71 found a significant difference (P < 0.01) individually among them and further observed packaging methods had no influence. [ABSTRACT FROM AUTHOR]

Summary: The properties of white meat, such as chicken and fish, changed quickly in the early postmortem period. This study focused on the relationship between myofibrillar protein and the eating quality of chicken in this period. The results showed that the eating quality of chicken, such as texture, water holding capacity and shear force value, decreased in the early postmortem period. The western blot analysis indicated that the desmin and troponin T were degraded significantly with postmortem time. Meanwhile, the myofibril protein degeneration in this period was evaluated by Fourier transform infrared and Differential Scanning Calorimetry. The findings demonstrated that the ordered structure of the myofibrillar protein was destroyed, and its thermal stability was reduced with the prolongation of postmortem time. Subsequently, the transmission electron microscope results suggested that the heating processing could destroy the connection between the weakened Z‐line and the myofilament. Overall, the decline in thermal stability and degradation of myofibrillar may worsen the structural instability of chicken during heating, which may be a significant contributor to the variations of chicken quality in the early postmortem period. [ABSTRACT FROM AUTHOR]

Fresh pork tenderness contributes to consumer satisfaction with the eating experience. Postmortem proteolysis of proteins within and between myofibrils has been closely linked with pork tenderness development. A clear understanding of the molecular features associated with pork tenderness development will provide additional targets and open the door to new solutions to improve and make pork tenderness development more consistent. Therefore, the objective was to utilize liquid chromatography and mass spectrometry with tandem mass tag (TMT) multiplexing to evaluate myofibrillar sub-proteome differences between pork chops of different instrumental star probe values. Pork loins (N = 120) were collected from a commercial harvest facility at 24 h postmortem. Quality and sensory attributes were evaluated at 24 h postmortem and after ~2 weeks of postmortem aging. Pork chops were grouped into 4 groups based on instrumental star probe value (group A,x¯ = 4.23 kg, 3.43 to 4.55 kg; group B,x¯ = 4.79 kg, 4.66 to 5.00 kg; group C,x¯ = 5.43 kg, 5.20 to 5.64 kg; group D,x¯ = 6.21 kg, 5.70 to 7.41 kg; n = 25 per group). Myofibrillar proteins from the samples aged ~2 wk were fractionated, washed, and solubilized in 8.3 M urea, 2 M thiourea, and 1% dithiothreitol. Proteins were digested with trypsin, labeled with 11-plex isobaric TMT reagents, and identified and quantified using a Q-Exactive Mass Spectrometer. Between groups A and D, 54 protein groups were differentially abundant (adjusted P < 0.05). Group A had a greater abundance of proteins related to the thick and thin filament and a lesser abundance of Z-line-associated proteins and metabolic enzymes than group D chops. These data highlight that distinct myofibrillar sub-proteomes are associated with pork chops of different tenderness values. Future research should evaluate changes immediately and earlier postmortem to further elucidate myofibrillar sub-proteome differences over the postmortem aging period. [ABSTRACT FROM AUTHOR]

Myofibrillar myopathy (MFM) is characterized by segmental disarray of myofibrils and ectopic accumulation of a protein called desmin. Previously thought to be a glycogen storage disease, MFM is now recognized as a stand-alone myopathy. Endurance Arabians with MFM usually present with exertional rhabdomyolysis (MFM-ER) at the end of races, elevated serum muscle enzymes, and myoglobinuria. Warmblood horses with MFM (MFM-WB) usually present with pain-associated behaviors such as exercise intolerance, reluctance to engage hind quarter muscles, shifting lameness and normal serum muscle enzymes. Both forms have evidence of decreased cysteine-based antioxidants and, additionally, MFM-WB has molecular signatures of a maladaptive training response., Competing Interests: Disclosure S.J. Valberg directs the Valberg Neuromuscular Disease laboratory (ValbergNMDL.com) and receives remuneration for analyzing muscle biopsy as well as royalties from the PSSM1 genetic test, the feed Re-Leve, and MFM pellet sold by Kentucky Equine Research. Z.J. Williams reports no conflict of interest., (Copyright © 2024 Elsevier Inc. All rights reserved.)

The study investigated the influence of the extrusion process variables on attributes of extrudates produced from three different mixes containing defatted soya alone or combined with meat myofibrillar or connective tissue protein. The mixes were extruded in a twin-screw co-rotating extruder using different screw configurations and independent process variables (die size, feed rate and screw speed). The characteristics of extruded products before and after retorting process were also examined. Extrudates produced from mixes containing 25% myofibrillar protein resulted in higher bulk density over the extrudates produced using defatted soya alone that resulted in low density and water absorption capacity. The screw configuration with the greatest number of reverse element sections resulted in the most expanded extrudates especially at the highest screw speed and the lowest feed rate. Overall, this study indicated that an appropriate selection of screw configuration and recipe mixes are essential to maximize the quality of the extruded products.

Gelation properties of myofibrillar protein (MP)/wheat gluten (WG) induced by glutamine transaminase (TGase) were studied. Results showed that the inclusion of transglutaminase increased the gel strength, water‐holding capacity (WHC), and nonfreezable water (Wnf) of MP/WG mixture. Circular dichroism (CD) analysis showed that the β‐sheet and random coil content of the MP/WG treated with TGase addition increased by 12.1% and 3.7%, while the α‐helix and β‐turn content decreased by 14.2% and 1.8%. Rheological measurements showed that TGase induced higher energy storage modulus value during the MP/WG gel heating‐cooling cycle. the hydrogen bond and hydrophobic interaction content of the MP/WG gels increased by 80 and 120 ug/L, and the disulfide bond decreased by 200 ug/L, with TGase addition was increased from 0 to 120 U/g protein. Scanning electron microscope (SEM) showed that MP/WG gel with TGase had uniform and dense network structure. Practical Application: The properties of myofibrillar/wheat gluten gel induced by TGase crosslinking was studied. The gel structure and water holding capacity of MP/WG were improved by the cross‐linking of TGase. The study of the gel properties of MP/WG induced by TGase crosslinking also can provide a theoretical basis for analyzing the effect of TGase on the application of gluten protein in complex meat emulsion system. [ABSTRACT FROM AUTHOR]

The objective of this study was to evaluate relationship with aggregation, secondary structures and gel properties of pork myofibrillar protein with different sodium chloride (1%, 2% and 3%). When the sodium chloride increased from 1 to 3%, the active sulfhydryl, surface hydrophobicity, hardness and cooking yield of myofibrillar protein were increased significantly (p < 0.05), the particle size, total sulfhydryl and Zeta potential were decreased significantly (p < 0.05), these meant the aggregations of pork myofibrillar protein were decreased. The changes of proteins aggregation induced the strongest intensity band of Amide I shifted up from 1660 cm−1 to 1661 cm−1, meanwhile, the β-sheet structure content was increased significantly (p < 0.05) with the sodium chloride increased. From the above, the lower proteins aggregation and higher β-sheet structure content could improve the water holding capacity and texture of pork myofibrillar protein gel. [ABSTRACT FROM AUTHOR]

Tenderness is an important indicator of meat quality, degradation plays important role during the maturation, therefore improving meat quality and tenderness. Understanding the process of myofibrillar and which enzymes affect degradation is more needed to prove. In this study we used longest muscle of Bashibai sheep of Xinjiang as the experiment material. The isolated myofibrillar protein and μ-calpains are incubated at 4°C about 1, 3, 7, 14, and 21 days using in vitro culture method and analysed by SDS-PAGE, Western blotting. Results showed that μ-calpain can improve the degradation of some myofibrillar proteins. Desmin was degraded by the 3rd, troponin-T was completely degraded by the 7th day.

This study aims to build a model for predicting the hardness of meat products by considering their protein fractions and protein structural changes during production. Protein solubility is considered an indicator of protein structural changes. The obtained model results show that structural changes of sarcoplasmic and myofibrillar proteins occur during production. The gelling capacity is formed by the effect of the three protein fractions, namely myofibrillar, sarcoplasmic and stromal. The obtained model allows the prediction of the hardness of meat products based on their protein fraction contents with error below 5%, thus reaching a significant adjustment between real process data and the simulated model. [ABSTRACT FROM AUTHOR]

The myosin-directed chaperone UNC-45B is essential for sarcomeric organization and muscle function from Caenorhabditis elegans to humans. The pathological impact of UNC-45B in muscle disease remained elusive. We report ten individuals with bi-allelic variants in UNC45B who exhibit childhood-onset progressive muscle weakness. We identified a common UNC45B variant that acts as a complex hypomorph splice variant. Purified UNC-45B mutants showed changes in folding and solubility. In situ localization studies further demonstrated reduced expression of mutant UNC-45B in muscle combined with abnormal localization away from the A-band towards the Z-disk of the sarcomere. The physiological relevance of these observations was investigated in C. elegans by transgenic expression of conserved UNC-45 missense variants, which showed impaired myosin binding for one and defective muscle function for three. Together, our results demonstrate that UNC-45B impairment manifests as a chaperonopathy with progressive muscle pathology, which discovers the previously unknown conserved role of UNC-45B in myofibrillar organization. [ABSTRACT FROM AUTHOR]

Key points: Respiratory muscle function declines with ageing, contributing to breathing complications in the elderly.Here we report greater in vitro respiratory muscle contractile function in old mice receiving supplemental NaNO3 for 14 days compared with age‐matched controls.Myofibrillar protein phosphorylation, which enhances contractile function, did not change in our study – a finding inconsistent with the hypothesis that this post‐translational modification is a mechanism for dietary nitrate to improve muscle contractile function.Nitrate supplementation did not change the abundance of calcium‐handling proteins in the diaphragm of old mice, in contrast with findings from the limb muscles of young mice in previous studies.Our findings suggest that nitrate supplementation enhances myofibrillar protein function without affecting the phosphorylation status of key myofibrillar proteins. Inspiratory muscle (diaphragm) function declines with age, contributing to ventilatory dysfunction, impaired airway clearance, and overall decreased quality of life. Diaphragm isotonic and isometric contractile properties are reduced with ageing, including maximal specific force, shortening velocity and peak power. Contractile properties of limb muscle in both humans and rodents can be improved by dietary nitrate supplementation, but effects on the diaphragm and mechanisms behind these improvements remain poorly understood. One potential explanation underlying the nitrate effects on contractile properties is increased phosphorylation of myofibrillar proteins, a downstream outcome of nitrate reduction to nitrite and nitric oxide. We hypothesized that dietary nitrate supplementation would improve diaphragm contractile properties in aged mice. To test our hypothesis, we measured the diaphragm function of old (24 months) mice allocated to 1 mm NaNO3 in drinking water for 14 days (n = 8) or untreated water (n = 6). The maximal rate of isometric force development (∼30%) and peak power (40%) increased with nitrate supplementation (P < 0.05). There were no differences in the phosphorylation status of key myofibrillar proteins and abundance of Ca2+‐release proteins in nitrate vs. control animals. In general, our study demonstrates improved diaphragm contractile function with dietary nitrate supplementation and supports the use of this strategy to improve inspiratory function in ageing populations. Additionally, our findings suggest that dietary nitrate improves diaphragm contractile properties independent of changes in abundance of Ca2+‐release proteins or phosphorylation of myofibrillar proteins. Key points: Respiratory muscle function declines with ageing, contributing to breathing complications in the elderly.Here we report greater in vitro respiratory muscle contractile function in old mice receiving supplemental NaNO3 for 14 days compared with age‐matched controls.Myofibrillar protein phosphorylation, which enhances contractile function, did not change in our study – a finding inconsistent with the hypothesis that this post‐translational modification is a mechanism for dietary nitrate to improve muscle contractile function.Nitrate supplementation did not change the abundance of calcium‐handling proteins in the diaphragm of old mice, in contrast with findings from the limb muscles of young mice in previous studies.Our findings suggest that nitrate supplementation enhances myofibrillar protein function without affecting the phosphorylation status of key myofibrillar proteins. [ABSTRACT FROM AUTHOR]

Muscle loss is a severe complication of many medical conditions such as cancer, cardiac failure, muscular dystrophies, and nerve damage. The contribution of myofibrillar protein synthesis (MPS) to the loss of muscle mass after nerve damage is not clear. Using deuterium oxide (D2O) labeling, we demonstrate that MPS is significantly increased in rat m.tibialis anterior (TA) compared to control (3.23 ± 0.72 [damaged] to 2.09 ± 0.26%∗day−1 [control]) after 4 weeks of nerve constriction injury. This is the case despite substantial loss of mass of the TA (350 ± 96 mg [damaged] to 946 ± 361 mg [control]). We also show that expression of regulatory proteins involved with MPS (p70s6k1: 2.4 ± 0.3 AU [damaged] to 1.8 ± 0.2 AU [control]) and muscle protein breakdown (MPB) (MAFbx: 5.3 ± 1.2 AU [damaged] to 1.4 ± 0.4 AU [control]) are increased in nerve damaged muscle. Furthermore, the expression of p70s6k1 correlates with MPS rates (r2 = 0.57). In conclusion, this study shows that severe muscle wasting following nerve damage is accompanied by increased as opposed to decreased MPS.

Background Oxidative stress and inflammation may contribute to anabolic resistance in response to protein and exercise in older adults. We investigated whether consumption of montmorency cherry concentrate (MCC) increased anabolic sensitivity to protein ingestion and resistance exercise in healthy older men. Methods Sixteen healthy older men were randomized to receive MCC (60 mL·d −1 ) or placebo (PLA) for two weeks, after baseline measures in week 1. During week 3, participants consumed 10 g whey protein·d −1 and completed three bouts of unilateral leg resistance exercise (4 × 8–10 repetitions at 80% 1RM). Participants consumed a bolus (150 mL) and weekly (50 mL) doses of deuterated water. Body water 2 H enrichment was measured in saliva and vastus lateralis biopsies were taken from the non-exercised leg after weeks 1, 2 and 3, and the exercised leg after week 3, to measure tracer incorporation at rest, in response to protein and protein + exercise. Results Myofibrillar protein synthesis increased in response to exercise + protein compared to rest (p < 0.05) in both groups, but there was no added effect of supplement (MCC: 1.79 ± 0.75 EX vs 1.15 ± 0.40 rest; PLA: 2.22 ± 0.54 vs 1.21 ± 0.18; all %·d −1 ). Muscle total NFĸB protein was decreased with exercise and protein in MCC (NFĸB: −20.7 ± 17.5%) but increased in PLA (NFĸB: 17.8 ± 31.3%, p = 0.073). Conclusion Short-term MCC ingestion does not affect the anabolic response to protein and exercise in healthy, relatively active, older men, despite MCC ingestion attenuating expression of proteins involved in the muscle inflammatory response to exercise, which may influence the chronic training response. [ABSTRACT FROM AUTHOR]

Muscle loss is a severe complication of many medical conditions such as cancer, cardiac failure, muscular dystrophies, and nerve damage. The contribution of myofibrillar protein synthesis (MPS) to the loss of muscle mass after nerve damage is not clear. Using deuterium oxide (D2O) labeling, we demonstrate that MPS is significantly increased in rat m. tibialis anterior (TA) compared to control (3.23 ± 0.72 [damaged] to 2.09 ± 0.26%∗day−1 [control]) after 4 weeks of nerve constriction injury. This is the case despite substantial loss of mass of the TA (350 ± 96 mg [damaged] to 946 ± 361 mg [control]). We also show that expression of regulatory proteins involved with MPS (p70s6k1: 2.4 ± 0.3 AU [damaged] to 1.8 ± 0.2 AU [control]) and muscle protein breakdown (MPB) (MAFbx: 5.3 ± 1.2 AU [damaged] to 1.4 ± 0.4 AU [control]) are increased in nerve damaged muscle. Furthermore, the expression of p70s6k1 correlates with MPS rates (r 2 = 0.57). In conclusion, this study shows that severe muscle wasting following nerve damage is accompanied by increased as opposed to decreased MPS. [ABSTRACT FROM AUTHOR]

Tenderness is an important indicator of meat quality, degradation plays important role during the maturation, therefore improving meat quality and tenderness. Understanding the process of myofibrillar and which enzymes affect degradation is more needed to prove. In this study we used longest muscle of Bashibai sheep of Xinjiang as the experiment material. The isolated myofibrillar protein and μ-calpains are incubated at 4°C about 1, 3, 7, 14, and 21 days using in vitro culture method and analysed by SDS-PAGE, Western blotting. Results showed that μ-calpain can improve the degradation of some myofibrillar proteins. Desmin was degraded by the 3rd, troponin-T was completely degraded by the 7th day. [ABSTRACT FROM AUTHOR]

Protein oxidation during chilling and frozen storage has recently attracted great attention due to its consequences on protein solubility and functionality. In this study, the effects of kappa-carrageenan oligosaccharides on myofibrillar protein oxidation in peeled shrimp ( Litopenaeus vannamei ) during frozen storage were investigated by assessing the content of the carbonyls, total sulfhydryl, dityrosine, and surface hydrophobicity. We also examined the means of antioxidant activity in vitro , degradation of muscle proteins, and integrity of tissue structure. Our data revealed that in vitro carrageenan oligosaccharides exhibited good capacities of OH , O 2 − , and DPPH· scavenging and Fe 2+ -chelating activity. Chemical analyses showed that frozen storage increased susceptibility of myofibrillar proteins to frozen oxidation. We found that the incorporation of carrageenan oligosaccharides during the treatment of the shrimp prior to frozen storage significantly decreased the formation of protein carbonyl and dityrosine, lowered the changes in myofibrillar surface hydrophobicity, and maintained a higher total sulfhydryl content when compared with the water-treated samples (control). Additionally, the results of protein degradation and tissue structure confirmed that these antioxidant oligosaccharides exhibited marked effects on stability of muscle proteins and effectively inhibited the degradation/oxidation of muscle proteins during frozen storage. Overall, the contribution of the antioxidant activities played an important role in cryoprotective effects of carrageenan oligosaccharides on frozen shrimp. Further application of these findings might maintain better quality and extend the commercialization of refrigerated products. [ABSTRACT FROM AUTHOR]

Copyright of Revista Brasileira de Saúde e Produção Animal (RBSPA) is the property of Revista Brasileira de Saude e Producao Animal (RBSPA) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The objective of this study was to investigate the microstructure, protein denaturation and water holding capacity of lamb pickled under pulse vacuum. Sixty topside samples (M. semimembranosus) were randomly assigned into two groups and cured for 0, 1.5, 3, 4.5 and 6 h by pulse vacuum brining (PVB) and atmospheric brining (AB) (control), respectively. The salt content of samples by PVB was about 1% higher than AB from 1.5 h to 6 h. The water holding capacity was greater for PVB group before 4.5 h ( P < 0.05). The actomyosin was dissolved more after being pickled for 1.5, 3, 4.5 and 6 h under PVB. The myofibril swelled more intensively and myofibril diameters with PVB were significantly larger than that of AB ( P < 0.05). In summary, pulse vacuum brining can be used to improve the brining efficiency, promoting the actomyosin dissociation and improving the water holding capacity of lamb, which will be a potential technology to be used in practice. [ABSTRACT FROM AUTHOR]

Myofibrillar myopathies are a genetically diverse group of skeletal muscle disorders, with distinctive muscle histopathology. Causative mutations have been identified in the genes MYOT, LDB3, DES, CRYAB, FLNC, BAG3, DNAJB6, FHL1, PLEC and TTN, which encode proteins which either reside in the Z-disc or associate with the Z-disc. Mitochondrial abnormalities have been described in muscle from patients with a myofibrillar myopathy. We reviewed the literature to determine the extent of mitochondrial dysfunction in each of the myofibrillar myopathy subtypes. Abnormal mitochondrial distribution is a frequent finding in each of the subtypes, but a high frequency of COX-negative or ragged red fibres, a characteristic finding in some of the conventional mitochondrial myopathies, is a rare finding. Few in vitro studies of mitochondrial function have been performed in affected patients. [ABSTRACT FROM AUTHOR]

The objective of this study was to determine the relationship between water-holding capacity (WHC) attributes and protein denaturation in broiler breast meat. Boneless skinless breast fillets (n = 72) were collected from a commercial processing plant at 2 h postmortem and segregated into low-WHC and high- WHC groups based on muscle pH and color (L*a*b*). At 6 and 24h postmortem, brine uptake (%), cooking loss (%), and protein solubility (sarcoplasmic and myofibrillar) were measured and protein fractions were analyzed using SDS-PAGE. Drip loss accumulation (%) was measured after storage for 2 and 7 days postmortem. High-WHC fillets exhibited lower LMightness values and greater pH values at 2 and 24 h postmortem than low-WHC fillets. High-WHC fillets had greater brine uptake and less cooking loss at both 6 and 24 h postmortem compared to low-WHC fillets. Aging from 6 to 24 h postmortem increased brine uptake in high- WHC fillets, but did not affect cooking loss in either low-WHC or high-WHC fillets. Drip loss accumulation was greater in low-WHC fillets at both 2 and 7 days postmortem. Myofibrillar protein solubility decreased with postmortem time but was not different between low-WHC and high-WHC fillets. Sarcoplasmic protein solubility increased with postmortem time and was greater in high-WHC fillets. SDS-PAGE analysis indicated that low-WHC fillets exhibited more glycogen phosphorylase denaturation than high-WHC fillets as evidenced by a more extensive shift of the protein from the sarcoplasmic to the myofibrillar protein fraction. Correlation analysis revealed that overall protein solubility measurements were not related to WHC attributes but that the degree of glycogen phosphorylase denaturation was significantly correlated (|r| = 0.52 to 0.80) to measures of WHC. Data indicated that WHC differences in broiler breast fillets were not due to differences in myofibrillar protein denaturation and suggested that the denaturation of sarcoplasmic proteins onto myofibrils may influence WHC in breast meat. [ABSTRACT FROM AUTHOR]

The catalytic capability of four commercially available food-grade fungal and bacterial protease preparations (AFP, FPII, F60K and HT) was evaluated over a range of pH, temperature and substrate conditions using esterase and caseinolytic activity assays and time course hydrolysis over 120 and 60 min of myofibrillar and connective tissue proteins, respectively. The protease preparations displayed similar casein hydrolysis kinetics and were active in hydrolysing BODIPY-FL casein to varying extents at postmortem aging meat pH (5.0–6.0). All of the four proteases exhibited selective hydrolytic activity towards meat myofibrillar proteins including myosin and actin. Significant hydrolysis of two meat tenderisation protein markers troponin T and desmin by the four proteases was detected by western blot. The results obtained indicate that the new fungal protease preparations AFP and FPII, bacterial protease preparation HT and the new source of fungal protease preparation F60K have potential for use in meat tenderising applications. [ABSTRACT FROM AUTHOR]

The major and minor allergens in fish and shellfish that have been identified are broadly spread in the myofibrillar and sarcoplasmic proteins. This study aimed to create a skin prick test reagent of crab myofibrillar and sarcoplasmic proteins to improve sensitivity and specificity diagnosis of allergy. Myofibrillar protein fraction was composed of 19 protein bands with the molecular weights of 9.6-111.6 kDa and sarcoplasmic protein fraction was composed of 19 protein bands with the molecular weights of 9.5-104.6 kDa. The allergenic myofibrillar protein has the molecular weights of 13.9-155.4 kDa while the allergenic sarcoplasmic protein has the molecular weights of 8.4-129.4 kDa. Crab myofibrillar and sarcoplasmic reagents met the requirements of the European Pharmacopoeia Monograph on Allergen Products 7 (2010:1063) for the parameters of moisture content, protein content, sterility and microbiology. A skin prick test to the respondents indicated that the sensitivity value of crab myofibrillar reagent was 85% and crab sarcoplasmic reagent was 69% with a negative error rate for each myofibrillar and sarcoplasmic reagents was 15% and 31%, respectively. The result diagnosis of crab myofibrillar and sarcoplasmic sensitivities would generate sensitivity value at 100%. The separation of crab proteins into myofibrils and sarcoplasm for skin prick test could improve its sensitivity value and lowered the negative misdiagnosis. The specificity of each myofibrillar and sarcoplasmic proteins was 100% with an error rate of positive diagnosis occurrence at 0%. [ABSTRACT FROM AUTHOR]

Highlights: [•] The trehalose enhanced Ca2+-ATPase activity compared to the control. [•] The trehalose enhanced myofibrillar solubility compared to the control. [•] The trehalose enhanced sulfhydryl content compared to the control. [ABSTRACT FROM AUTHOR]

Abstract: Properties and storage stability of two different jumbo squid myofibrillar protein-based films were investigated. Myofibrillar proteins were extracted by isoelectric precipitation after acidic and alkaline solubilization, obtaining the same extraction yield. During extraction the edible fraction, which was discarded during mantle skinning, was recovered, and the fishy flavour produced by nitrogen and other undesirable compounds was removed, although some sarcoplasmic proteins were lost simultaneously. In alkaline-Concentrate (C), myosin unfolding led to water resistant films, less water vapour permeable and more mechanically resistant than acidic–Films (F); whereas acidic-C protein hydrolysis resulted in more transparent and soluble films, with higher protein release (∼80 g/L). During 4 months of storage some structure reorganization occurred, and both films incremented their yellowish tendency, especially the acidic-F, being this attributed to a Maillard reaction with plasticizers. After storage time, water solubility increased in C-films. While acidic-F aggregation led to a protein release reduction and tensile strength improvement, alkali-F became weak and brittle, loosing transparency. C-films offered different filmogenic properties, proving to be promising biodegradable packaging materials. [Copyright &y& Elsevier]

A large Italo- Spanish kindred with autosomal-dominant inheritance has been reported with proximal limb and axial muscle weakness. Clinical, histological and genetic features have been described. A limb girdle muscular dystrophy 1 F ( LGMD1F) disease locus at chromosome 7q32.1-32.2 has been previously identified. We report a muscle pathological study of two patients (mother and daughter) from this family. Muscle morphologic findings showed increased fiber size variability, fiber atrophy, and acid-phosphatase-positive vacuoles. Immunofluorescence against desmin, myotilin, p62 and LC3 showed accumulation of myofibrils, ubiquitin binding protein aggregates and autophagosomes. The ultrastructural study confirmed autophagosomal vacuoles. Many alterations of myofibrillar component were detected, such as prominent disarray, rod-like structures with granular aspect, and occasionally, cytoplasmic bodies. Our ultrastructural data and muscle pathological features are peculiar to LGMD1F and support the hypothesis that the genetic defect leads to a myopathy phenotype associated with disarrangement of the cytoskeletal network. [ABSTRACT FROM AUTHOR]

Early-onset myopathy, areflexia, respiratory distress, and dysphagia (EMARDD) is caused by homozygous or compound heterozygous mutation in the MEGF10 gene (OMIM #614399). Phenotypic spectrum of EMARDD is variable, ranging from severe infantile forms in which patients are ventilator-dependent and die in childhood, to milder chronic disorders with a more favorable course (mild variant, mvEMARDD). Here we describe a 22 years old boy, offspring of consanguineous parents, presenting a congenital myopathic phenotype since infancy with elbow contractures and scoliosis. The patient developed a slowly progressive muscle weakness with impaired walking, rhinolalia, dysphagia, and respiratory involvement, which required noninvasive ventilation therapy since the age of 16 years. First muscle biopsy revealed unspecific muscle damage, with fiber size variation, internal nuclei and fibrosis. Myofibrillar alterations were noted at a second muscle biopsy including whorled fibres, cytoplasmic inclusion and minicores. Exome sequencing identified a homozygous mutation in MEGF10 gene, c.2096G > C (p.Cys699Ser), inherited by both parents. This variant, not reported in public databases of mutations, is expected to alter the structure of the protein and is therefore predicted to be probably damaging according to ACMG classification. In conclusion, we found a new likely pathogenic mutation in MEGF10 , which is responsible for a progressive form of mvEMARDD with myofibrillar alterations at muscle biopsy. Interestingly, the presence of MEGF10 mutations has not been reported in Italian population. Early diagnosis of MEGF10 myopathy is essential in light of recent results from in vivo testing demonstrating a potential therapeutic effect of SSRIs compounds., (©2022 Gaetano Conte Academy - Mediterranean Society of Myology, Naples, Italy.)

Abstract: Proteomic approaches have been used to identify the main proteins present in processing by-products generated by the canning tuna-industry, as well as in by-products derived from filleting of skeletal red muscle of fresh tuna. Following fractionation by using an ammonium sulphate precipitation method, three proteins (tropomyosin, haemoglobin and the stress-shock protein ubiquitin) were identified in the highly heterogeneous and heat-treated material discarded by the canning-industry. Additionally, this fractionation method was successful to obtain tropomyosin of high purity from the heterogeneous starting material. By-products from skeletal red muscle of fresh tuna were efficiently fractionated to sarcoplasmic and myofibrillar fractions, prior to the identification based mainly on the combined searching of the peptide mass fingerprint (MALDI–TOF) and peptide fragment fingerprinting (MALDI LIFT-TOF/TOF) spectra of fifteen bands separated by 1D SDS–PAGE. Thus, the sarcoplasmic fraction contained myoglobin and several enzymes that are essential for efficient energy production, whereas the myofibrillar fraction had important contractile proteins, such as actin, tropomyosin, myosin or an isoform of the enzyme creatine kinase. Application of proteomic technologies has revealed new knowledge on the composition of important by-products from tuna species, enabling a better evaluation of their potential applications. [Copyright &y& Elsevier]

Exercise is not only associated with adaptive responses within skeletal muscle fibers but also with induction of collagen synthesis both in muscle and adjacent connective tissue. Additionally, exercise and training leads to activation of the systemic growth hormone/insulin-like growth factor I axis ( GH/IGF-I), as well as increased local IGF-I expression. Studies in humans with pathologically high levels of GH/IGF-I, and in healthy humans who receive either weeks of GH administration or acute injection of IGF-I into connective tissue, demonstrate increased expression and synthesis of collagen in muscle and tendon. These observations support a stimulatory effect of GH/IGF-I on the connective tissue in muscle and tendon, which appears far more potent than the effect on contractile proteins of skeletal muscle. However, GH/IGF-I may play an additional role in skeletal muscle by regulation of stem cells (satellite cells), as increased satellite cell numbers are found in human muscle with increased GH/IGF-I levels, despite no change in myofibrillar protein synthesis. Although advanced age is associated with both a reduction in the GH/IGF-I axis activity, and in skeletal muscle mass (sarcopenia) as well as in tendon connective tissue, there is no direct proof linking age-related changes in the musculotendinous tissue to an impaired GH/IGF-I axis. [ABSTRACT FROM AUTHOR]

It is often recommended that heavier training intensities (∼70%-80% of maximal strength) be lifted to maximize muscle growth. However, we have reported that intensities as low as 30% of maximum strength, when lifted to volitional fatigue, are equally effective at stimulating muscle protein synthesis rates during resistance exercise recovery. This paper discusses the idea that high-intensity contractions are not the exclusive driver of resistance exercise-induced changes in muscle protein synthesis rates. [ABSTRACT FROM AUTHOR]

Abstract: Gelation properties of mixtures of myofibrillar protein isolate (MPI)/pea protein isolate (PPI) were studied using a dynamic oscillatory rheometer and a texture analyzer to evaluate PPI as a possible meat product additive. The inclusion of microbial transglutaminase (MTG) increased the gel strength of MPI/PPI mixture (3% + 1%) more than it did for MPI (3%), but less than a 3% MPI, 1% soy protein isolate combination. The direct evidence of interaction between muscle and pea proteins in the form of new sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) bands was not found; however, the improvement in gel strength or gel peak force for the MPI/PPI mixture (3% + 1%) with inclusion of MTG suggested that some ɛ (γ-glutamyl) lysine (G-L) crosslinking occurred between muscle and pea proteins. It likely that pea protein acted as a non-gelling component and interspersed throughout the primary MPI gel network and the addition of MTG promoted partial crosslinking of MPI. Consequently, MTG is useful in improving gelation properties of heat-induced MPI/PPI gel. [Copyright &y& Elsevier]

Abstract: This study investigated the effects of microbial transglutaminase (TG) on structural changes in porcine myofibrillar protein (MP) under varying pH (2.0–6.0) and two ionic strength conditions (0.1M versus 0.6M NaCl). Lowering the pH below the isoelectric point (pI) of myosin induced protein unfolding as revealed by surface hydrophobicity and differential scanning calorimetry. Although the MP solubility at the low ionic strength (0.1M NaCl) was maximal at pH 3.0, both SDS-PAGE profiles and dynamic rheology indicated TG could not cross-link MP under this condition. Based on the carboxyl group content, the TG-catalyzed deamidation was dominant at a pH lower than the pI of myosin (pH 5.0) while cross-linking occurred at higher pH. Moreover, deamidation had no effect on rheological properties of MP. The results indicate that the TG reaction was governed by the pH of substrate protein, and the reaction intensity was related to the solubility of protein. [Copyright &y& Elsevier]

Abstract: In this study, the effects of microbial transglutaminase (MTG) and calcium alginate (CA) systems in combination with soybean oil on the emulsion properties of porcine myofibrillar protein (MP) were evaluated under various pH conditions. MTG was shown to improve emulsifying capacity and creaming stability, which increased with increasing pH values up to 6.5. The CA did not influence emulsifying capacity, but it improved the creaming stability of the MP-stabilized emulsions. Both MTG and CA enhanced the rheological properties, but their effects on the physical characteristics of the protein evidenced an opposite trend in relation to pH, i.e., the MTG system improved both the emulsion and gelling properties with increasing pH, whereas the CA system was effective when the pH was lowered. By combining the two MP gelling systems, a stable and pH-insensible emulsion could be produced. [Copyright &y& Elsevier]

In 1974, Markesbery et al. thoroughly characterized and reported a large kindred with distal muscle weakness of late adult-onset that was autosomal dominantly inherited. Clinical evidence supported myopathy rather than the usual neuropathy expected with distal weakness. Postmortem examination of two patients documented myopathy and excluded anterior horn cell disease or peripheral neuropathy as the cause. Distinctive morphologic changes were present in muscle. Widely accepted as a distinct disease entity, this disorder has recently been characterized as one of a group of myofibrillar myopathies resulting from mutations in several muscle proteins. Studies of members of the original family have now identified the molecular defect to be a mutation in ZASP, Z-band alternatively spliced PDZ-motif-containing protein. The specific mutation, A165V, was identified in all clinical affected family members by direct sequencing. Thus, Markesbery disease is a zaspopathy. Other families have been identified with the same mutation and a shared haplotype indicating a founder effect. [ABSTRACT FROM AUTHOR]

The mixed protein gels were prepared adding soy protein isolate (SPI), 7S globulin, enzyme-hydrolyzed soy proteins, 10- to 100-kDa ultrafiltration fraction and 0.5- to 10-kDa ultrafiltration fraction to myofibril protein isolate (MPI) gels, and five chemical interactions namely nonspecific associations, ionic bonds, hydrogen bonds, hydrophobic interactions and disulfide bonds in these gels were investigated by means of determining gel solubility within 20–75 °C. Furthermore, correlations between gel strength and different chemical interactions were evaluated statistically by Pearson’s correlation test. The gels with 0.5- to 10-kDa fraction presented the biggest gel strength below 60 °C, and the gels with SPI had better gel strength above 65 °C. At different endpoint temperatures, nonspecific associations decreased in order of MPI mixed with 0.5- to 10-kDa fraction, 10- to 100-kDa fraction, enzyme-hydrolyzed soy proteins, 7S globulin and SPI. Gels with ultrafiltration fractions had higher ionic bonds. Hydrogen bonds fluctuated in small scale below 55 °C and reduced at higher temperature. Hydrophobic interactions increased to maximum before decreasing slowly as the temperature went on. In short, both hydrophobic interactions and ionic bonds had significantly positive correlation with gel strength for mixed gels with enzyme-hydrolyzed soy proteins, whereas for the other four mixed gels, it was hydrophobic interactions and nonspecific associations. [ABSTRACT FROM AUTHOR]

Background: Chronic alcohol abuse contributes not only to an increased risk of health-related complications, but also to a premature mortality in adults. Myocardial dysfunction, including the development of a syndrome referred to as alcoholic cardiomyopathy, appears to be a major contributing factor. One mechanism to account for the pathogenesis of alcoholic cardiomyopathy involves alterations in protein expression secondary to an inhibition of protein synthesis. However, the full extent to which myocardial proteins are affected by chronic alcohol consumption remains unresolved. Methods: The purpose of this study was to examine the effect of chronic alcohol consumption on the expression of cardiac proteins. Male rats were maintained for 16 weeks on a 40% ethanol-containing diet in which alcohol was provided both in drinking water and agar blocks. Control animals were pair-fed to consume the same caloric intake. Heart homogenates from control- and ethanol-fed rats were labeled with the cleavable isotope coded affinity tags (ICAT™). Following the reaction with the ICAT™ reagent, we applied one-dimensional gel electrophoresis with in-gel trypsin digestion of proteins and subsequent MALDI-TOF-TOF mass spectrometric techniques for identification of peptides. Differences in the expression of cardiac proteins from control- and ethanol-fed rats were determined by mass spectrometry approaches. Results: Initial proteomic analysis identified and quantified hundreds of cardiac proteins. Major decreases in the expression of specific myocardial proteins were observed. Proteins were grouped depending on their contribution to multiple activities of cardiac function and metabolism, including mitochondrial-, glycolytic-, myofibrillar-, membrane-associated, and plasma proteins. Another group contained identified proteins that could not be properly categorized under the aforementioned classification system. Conclusions: Based on the changes in proteins, we speculate modulation of cardiac muscle protein expression represents a fundamental alteration induced by chronic alcohol consumption, consistent with changes in myocardial wall thickness measured under the same conditions. [ABSTRACT FROM AUTHOR]

The objective of the study was to investigate the role of hydrolyzed potato protein (HPP) in protecting myofibril protein isolate (MPI) from oxidative modification. MPI prepared from pork muscle was suspended (30 mg protein/mL) in 15 mM piperazine- N, N-bis(2-ethane sulfonic acid) buffer (pH 6.0) with 0, 0.3, 0.75, and 1.5 mg/mL of antioxidative HPP (1-h Alcalase hydrolysate). Oxidation was induced by incubating the protein suspensions at 4 °C for 24 h with (1) an iron-catalyzed oxidizing system (IOS: 0.01 mM FeCl3, 0.1 mM ascorbic acid, and 1.0 mM H2O2) and (2) a metmyoglobin-oxidizing system (MOS: 0.1 mM metmyoglobin and 0.1 mM H2O2). Changes in oxidized MPI were measured as thiobarbituric acid-reactive substances (TBARS), protein carbonyl content, Ca- and K-ATPase activities, and ultraviolet (UV) spectra. Oxidation increased the production of TBARS and protein carbonyls by 2.9- and 0.24-fold in IOS and 5.6- and 2.2-fold in MOS, respectively. The 2 oxidizing systems altered the Ca- and K-ATPase activities and exposed hydrophobic groups buried in MPI. The presence of HPP reduced the extent of MPI oxidation in all physicochemical categories tested. Therefore, HPP may be used as a potential functional ingredient in meat products to enhance their oxidative stability. [ABSTRACT FROM AUTHOR]

We hypothesized a differential activation of the anabolic signaling proteins protein kinase B (PKB) and p70 S6 kinase (p70S6K) and subsequent differential stimulation of human muscle protein synthesis (MPS) after dynamic shortening or lengthening exercise. Eight healthy men [25 ± 5 yr, BMI 26 ± 3 kg/m-2 (means ± SD)] were studied before and after 12 min of repeated stepping up to knee height, and down again, while carrying 25% of their body weight, i.e., shortening exercise with the ‘up’ leg and lengthening exercise with contralateral ‘down’ leg. Quadriceps biopsies were taken before and 3, 6, and 24 h after exercise. After exercise, over 2 h before the biopsies, the subjects ingested 500 ml of water containing 45 g of essential amino acids and 135 g of sucrose. Rates of muscle protein synthesis were determined via incorporation over time of [1-13C]leucine (≤6 h after exercise) or [1-13C]valine (21–24 h after exercise) and phosphorylation of signaling proteins by Western analysis. PKB and p70S6K phosphorylation increased ∼3-fold after 3 h and remained elevated at 6 and 24 h. After exercise, rates of myofibrillar and sarcoplasmic protein synthesis were unchanged over the period including exercise and 3 h of recovery but had increased significantly at 6 (∼3.0- and 2.4-fbld, respectively) and 24 h (∼3.2- and 2.0-fold, respectively), independently of the mode of exercise. Short-term dynamic exercise in either shortening or lengthening mode increases MPS at least as much as resistance exercise and is associated with long-term activation of PKB and p70S6K. [ABSTRACT FROM AUTHOR]

Measurement of myocardial concentration of the myofibrillar protein, cardiac troponin T (cTnT), was used as a biochemical correlate of myocardial myofibrillar volume fraction to confirm and extend results of histomorphometric studies of changes in myofibrillar density during hypertrophy. Rat models were used to study concentric cardiac hypertrophy due to pressure overload (spontaneous hypertension), eccentric cardiac hypertrophy due to volume overload (administration of minoxidil for 4 weeks), and mixed cardiac hypertrophy due to growth factor stimulation (administration of triiodothyronine for 4 weeks). Mean myocardial cTnT concentration was 583±60 µg/g wet weight tissue in 40 control rats aged 10-20 weeks. We confirmed that pressure overload increased myofibrillar density by up to 30%, whereas volume overload decreased myofibrillar density, in our study, by up to 15%. Growth factor-induced hypertrophy was confirmed to occur by a mixture of processes; while myofibrillar density had increased by 31% at 1 week, it had normalised by 4 weeks. Minoxidil-induced hypertrophy was also confirmed to occur by a mixture of the processes, with myofibrillar density first decreased by 15% at 1 week before normalising by 4 weeks. Progressive, pathological hypertrophy, as modelled with spontaneous hypertension, was confirmed to be associated with abnormal myocardial myofibrillar density. We conclude that myocardial cTnT concentration may be used as a simple and precise biomarker of myofibrillar volume density, which, assessed over time, discriminates early physiological mechanisms involving myocyte thickening from those involving myocyte elongation and may discriminate between physiological and pathological hypertrophy. [ABSTRACT FROM AUTHOR]

A 1-year-old male neutered Australian Shepherd dog was referred to a veterinary specialist for evaluation of chronic lameness, contractures, and exercise intolerance. Serum creatine kinase was elevated, and electromyography showed complex repetitive discharges. Cardiomyopathy was clinically identified. Muscle biopsies evaluated by light and electron microscopy, and immunohistochemistry revealed the presence of a myofibrillar myopathy with accumulation of desmin and other proteins. These observations represent the first report of myofibrillar myopathy in the dog. [Copyright &y& Elsevier]

Functional properties of muscle proteins of volador (Illex coindetii) were evaluated during frozen storage and classified according to gender and anatomical part of the animal. Solubility of protein in 5% NaCl, in all lots, showed a significant increase in the initial months and then a decrease. This solubility was generally greater in the mantles than in the arms. The viscosity was initially very high and fell rapidly, and there were no significant differences between the lots. This initial viscosity was greater in the arm lots than in the mantle ones. Likewise, extracts of the muscle of the arms also had the greatest initial emulsifying capacity values (P&les;0.05). Soluble collagen, in an acid medium-exhibited a similar trend in all lots, throughout frozen storage. At the early stages of storage, soluble collagen remained stable or increased slightly, and then tended to become insoluble. The lowest solubilities were for the muscles of the arms. Myofibrillar protein and collagen solubilities, as well as emulsifying capacities were effective for detecting molecular changes in the proteins during frozen storage and results showed that, the volador mantles were more suited to frozen storage than the arms. [Copyright &y& Elsevier]