Sarcoplasmic Proteins Research Articles

The first evidence of global meat phosphoproteome changes in response to pre-slaughter stress

BackgroundPre-slaughter stress (PSS) impairs animal welfare and meat quality. Dark, firm and dry (DFD) are terms used to designate poor quality meats induced by PSS. Protein phosphorylation can be a potentially significant mechanism to explain rapid and multiple physiological and biochemical changes linked to PSS-dependent muscle-to-meat conversion. However, the role of reversible phosphorylation in the response to PSS is still little known. In this study, we report a comparative phosphoproteomic analysis of DFD and normal meats at 24 h post-mortem from the longissimus thoracis (LT) bovine muscle of male calves of the Rubia Gallega breed. For this purpose, two-dimensional gel electrophoresis (2-DE), in-gel multiplex identification of phosphoproteins with PRO-Q Diamond phosphoprotein-specific stain, tandem (MALDI-TOF/TOF) mass spectrometry (MS), novel quantitative phosphoproteomic statistics and bioinformatic tools were used.ResultsNoticeable and statistically significant differences in the extent of protein phosphorylation were detected between sample groups at the qualitative and quantitative levels. Overall phosphorylation rates across significantly changed phosphoproteins were about three times higher in DFD than in normal meat. Significantly changed phosphoproteins involved a variable number of isoforms of 13 myofibrillar and sarcoplasmic nonredundant proteins. However, fast skeletal myosin light chain 2 followed by troponin T, F-actin-capping and small heat shock proteins showed the greatest phosphorylation change, and therefore they were the most important phosphoproteins underlying LT muscle conversion to DFD meat in the Rubia Gallega breed.ConclusionsThis is the first study reporting global meat phosphoproteome changes in response to PSS. The results show that reversible phosphorylation is a relevant mechanism underlying PSS response and downstream effects on meat quality. This research opens up novel horizons to unravel the complex molecular puzzle underlying muscle-to-meat conversion in response to PSS.

CPVT: Arrhythmogenesis, Therapeutic Management, and Future Perspectives. A Brief Review of the Literature.

Catecholaminergic Polymorphic Ventricular Tachycardia (CPVT) is a primary electrical disease characterized by a normal resting electrocardiogram and induction of malignant arrhythmias during adrenergic stress leading to syncope or sudden cardiac death (SCD). CPVT is caused by mutations in the cardiac ryanodine receptor (RyR2) or in the sarcoplasmic reticulum protein calsequestrin 2 genes (CASQ2). The RyR2 mutations are responsible for the autosomal dominant form of CPVT, while CASQ2 mutations are rare and account for the recessive form. These mutations cause a substantial inballance in the homeostasis of intracellular calcium resulting in polymorphic ventricular tachycardia through triggered activity. Beta blockers were for years the cornerstone of therapy in these patients. Sodium channel blockers, especially flecainide, have an additive role in those not responding in beta blockade. Implantation of defibrillators needs a meticulous evaluation since inappropriate shocks may lead to electrical storm. Finally, cardiac sympathetic denervation might also be an alternative therapeutic option. Early identification and risk stratification is of major importance in patients with CPVT. The aim of the present review is to present the arrhythmogenic mechanisms of the disease, the current therapies applied and potential future perspectives.

Technological and safety characterization of coagulase-negative staphylococci with high protease activity isolated from Traditional Chinese fermented sausages

The aim of this study was to determine the technological and safety properties of coagulase-negative staphylococci (CNS) with high protease activity isolated from traditional Chinese fermented sausages in 10 different regions. According to the criteria of meat starter cultures, eight strains were obtained from 76 Gram-positive and catalase-positive isolates of CNS. These strains could hydrolyze both sarcoplasmic and myofibrillar proteins, tolerate 10% of salts and 150 mg/kg nitrites, possessed good nitrate reductase activity and lipolytic activity, and exhibited non-decarboxylase activity. Furthermore, all the eight strains exhibited antibiotic susceptibilities and negative hemolytic activity, DNase activity, and biofilm formation ability. Whole genome sequencing demonstrated that there were no pathogenic genes in the eight CNS strains, including 18 enterotoxin genes, panton-valentine leukocidin, toxic shock syndrome toxin-1, exfoliative toxin genes, and biofilm genes. Based on the results of API and 16S rRNA sequence analysis, seven of the eight CNS strains were identified as Staphylococcus simulans and the remaining one was S. saprophyticus.

Phosphorylation of sarcoplasmic and myofibrillar proteins in three ovine muscles during postmortem ageing

This study aimed to examine changes in phosphorylation of sarcoplasmic and myofibrillar proteins from longissimus lumborum, semitendinosus, and psoas major muscles during postmortem ageing for 5 d. These sarcoplasmic and myofibrillar proteins were separated using sodium dodecyl sulfate-polyacrylamide gel electrophoresis and stained with phosphorous and protein specific stains. Myofibril fragmentation index, pH, the content of lactic acid and the relative activity of μ-calpain in three ovine muscles were measured. These results showed that the relative phosphorylation level of sarcoplasmic and myofibrillar proteins of psoas major muscle were lower compared with longissimus lumborum and semitendinosus muscles (P<0.05). The pH of psoas major muscle was the lowest at 0.5 h postmortem, and the highest after 12 h postmortem (P<0.05). In addition, the relative activity of μ-calpain was higher within 5 d postmortem and myofibril fragmentation index was higher after 1 d postmortem in psoas major muscle than those of longissimus lumborum and semitendinosus muscles (P<0.05). The sarcoplasmic protein phosphorylation may regulate the rate of pH decline to influence the μ-calpain activity and then proteolysis of proteins consequently. This study gives a new perspective of the mechanism of postmortem meat tenderization.

On the origin of thaw loss: Relationship between freezing rate and protein denaturation

The role of protein denaturation in formation of thaw loss is currently not well understood. This study investigated denaturation of myofibrillar and sarcoplasmic proteins of pork loins caused by freezing-thawing in relation to freezing rate. Compared to fast freezing, slow freezing caused 28% larger thaw loss, decreased water-holding capacity of myofibrils and increased surface hydrophobicity, indicating more pronounced denaturation of myofibrillar proteins. We here propose a model: In slow freezing protons are concentrated in the unfrozen water resulting in reduced pH in proximity of structural proteins causing protein denaturation. In parallel, large ice crystals are formed outside of muscle fibers resulting in transversal shrinkage. In fast freezing small ice crystals trap protons and cause less severe protein denaturation and reduced thaw loss. Differential scanning calorimetry and tryptophan fluorescence spectra indicated sarcoplasmic protein denaturation in drip due to freezing-thawing. However, sarcoplasmic protein denaturation was independent of freezing rate.

Defining specific allergens for improved component-resolved diagnosis of shrimp allergy in adults

Shrimp is one of the predominant causes of food allergy among adults, often presenting with severe reactions. Current in vitro diagnostics are based on quantification of patient specific-IgE (sIgE) to shrimp extract. Tropomyosin is the known major shrimp allergen, but IgE sensitisation to other allergens is poorly characterised.In this study, the binding of IgE to various shrimp allergens, additional to tropomyosin, was investigated using sera from 21 subjects who had clinical reactions to one or more shellfish species. Total shrimp-sIgE was quantified using ImmunoCAP, while allergen-sIgEs were quantified using immunoblotting and mass spectrometry, and immuno-PCR to recombinant shrimp tropomyosin.Sixty-two percent of subjects (13/21) were positive to shrimp by ImmunoCAP. IgE from 43% of subjects (9/21) bound tropomyosin, while an additional 29% of subjects (6/21) demonstrated IgE-binding solely to other shrimp allergens, including sarcoplasmic calcium-binding protein, arginine kinase and hemocyanin. Furthermore, IgE sensitisation to other shrimp allergens was demonstrated in 50% of subjects (4/8) who were ImmunoCAP negative.The lack of standardised shrimp allergens and inadequacy of current extracts for shrimp allergy diagnosis is highlighted by this study. Comprehensive knowledge of less studied allergens and their inclusion in component-resolved diagnostics will improve diagnostic accuracy, benefitting the wider population suffering from shellfish allergy.

Physico‐chemical and proteolytic changes during cold storage of dry‐cured pork loins with probiotic strains of LAB

SummarySelected physico‐chemical and proteolysis‐related parameters were evaluated in dry‐cured loins inoculated with probiotic (Lactobacillus rhamnosus LOCK900, Bifidobacterium animalis subsp. lactis BB12) and potentially probiotic (Lactobacillus acidophilus Bauer Ł0938) lactic acid bacteria (LAB) strains and compared with a control sample at five different storage times (28, 90, 180, 270 and 360 days). Physico‐chemical parameters of dry‐cured loins were significantly (P &lt; 0.01) affected by treatment, storage time and the interaction between them. The count of lactic acid bacteria (LAB) in dry‐cured loins was in accordance with their pH. Higher intensity of proteolysis, as assessed by non‐protein nitrogen content (NPN) and proteolysis index (PI), occurred in inoculated samples. Based on the SDS‐PAGE analysis, the modifications produced during storage on the sarcoplasmic proteins were more pronounced than those exerted on the myofibrillar protein fraction. However, inoculation effect was absent from SDS‐PAGE protein patterns.

Purification and biochemical characteristics of the protease from Lactobacillus brevis R4 isolated from Harbin dry sausages

This study investigated the purification and biochemical characteristics of the protease secreted by Lactobacillus brevis R4 that was isolated from Harbin dry sausages. The optimized fermentation conditions were a fermentation time of 36 h, an initial pH of 5 and a fermentation temperature of 42 °C. A 27.9 kDa extracellular protease was purified using ammonium sulfate precipitation, ion exchange layer and gel filtration and was determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The protease produced by L. brevis R4 reached the highest relative protease activity at pH 7, 35 °C and 36 h. The microbial protease activity was inhibited by Zn2+, Cu2+ ions and ethylene diamine tetraacetic acid disodium salt (EDTA). The maximum velocity of the reaction (Vmax) and Michaelis constant (Km) of the protease were 65.9 mg/min and 17.1 mg/mL, respectively. SDS-PAGE demonstrated the ability of the protease to hydrolyse myofibrillar and sarcoplasmic proteins, especially on the myosin heavy chain, paramyosin, troponin, myosin light chain and glyceraldehyde dehydrogenase. The study provides a basis for understanding the enzymatic properties of the L. brevis R4 protease. In conclusion, L. brevis R4 has the potential to be used as a starter culture or protease-producing strain to produce Harbin dry sausages.

Muscle fiber hypertrophy in response to 6 weeks of high-volume resistance training in trained young men is largely attributed to sarcoplasmic hypertrophy.

Cellular adaptations that occur during skeletal muscle hypertrophy in response to high-volume resistance training are not well-characterized. Therefore, we sought to explore how actin, myosin, sarcoplasmic protein, mitochondrial, and glycogen concentrations were altered in individuals that exhibited mean skeletal muscle fiber cross-sectional area (fCSA) hypertrophy following 6 weeks of high-volume resistance training. Thirty previously resistance-trained, college-aged males (mean ± standard deviation: 21±2 years, 5±3 training years) had vastus lateralis (VL) muscle biopsies obtained prior to training (PRE), at week 3 (W3), and at week 6 (W6). Muscle tissue from 15 subjects exhibiting PRE to W6 VL mean fCSA increases ranging from 320–1600 μm2 was further interrogated using various biochemical and histological assays as well as proteomic analysis. Seven of these individuals donated a VL biopsy after refraining from training 8 days following the last training session (W7) to determine how deloading affected biomarkers. The 15 fCSA hypertrophic responders experienced a +23% increase in mean fCSA from PRE to W6 (p<0.001) and, while muscle glycogen concentrations remained unaltered, citrate synthase activity levels decreased by 24% (p<0.001) suggesting mitochondrial volume decreased. Interestingly, repeated measures ANOVAs indicated that p-values approached statistical significance for both myosin and actin (p = 0.052 and p = 0.055, respectively), and forced post hoc tests indicated concentrations for both proteins decreased ~30% from PRE to W6 (p<0.05 for each target). Phalloidin-actin staining similarly revealed actin concentrations per fiber decreased from PRE to W6. Proteomic analysis of the sarcoplasmic fraction from PRE to W6 indicated 40 proteins were up-regulated (p<0.05), KEGG analysis indicated that the glycolysis/gluconeogenesis pathway was upregulated (FDR sig. <0.001), and DAVID indicated that the following functionally-annotated pathways were upregulated (FDR value <0.05): a) glycolysis (8 proteins), b) acetylation (23 proteins), c) gluconeogenesis (5 proteins) and d) cytoplasm (20 proteins). At W7, sarcoplasmic protein concentrations remained higher than PRE (+66%, p<0.05), and both actin and myosin concentrations remained lower than PRE (~-50%, p<0.05). These data suggest that short-term high-volume resistance training may: a) reduce muscle fiber actin and myosin protein concentrations in spite of increasing fCSA, and b) promote sarcoplasmic expansion coincident with a coordinated up-regulation of sarcoplasmic proteins involved in glycolysis and other metabolic processes related to ATP generation. Interestingly, these effects seem to persist up to 8 days following training.

Effect of temperature on the actomyosin-paramyosin structure from giant squid mantle (Dosidicus gigas).

The secondary structure of a protein determines its functional properties, such as its gelling capacity. The α-helix and β-sheet comprise its main structures. Myofibrillar proteins from jumbo squid are composed mainly of the actomyosin-paramyosin complex; this complex contains a high percentage of α-helix, because actin, paramyosin, and myosin constitute 30%, 100%, and 55% of the α-helix, respectively. It is important to elucidate the role of the secondary structures in the gelation of giant squid proteins as they form gel. The role of the secondary structures in the gelation of giant squid proteins is therefore very important. For this reason, the objective of this work was to evaluate the effect of temperature on the structural behavior of actomyosin-paramyosin isolate (API) from Dosidicus gigas. The unfolding of the API system, which is composed of the actomyosin-paramyosin complex, was clarified by studying surface hydrophobicity and viscosity. Three characteristic peaks were found, associated with myosin, paramyosin, and actin. Infrared and circular dichroism corroborated the view that API undergoes major structural changes, because it proceeds from mostly an α-helix structure to 100% β-sheet. The structural rearrangement favors gelation by cross-linking, generating new protein-protein and water-protein interactions, which create a more stable structure compared to mantle proteins (MP). Likewise, the presence of sarcoplasmic and stromal proteins in D. gigas muscle prevents the unfolding of myofibrillar proteins, favoring gelation by agglomeration, decreasing the ability to trap water and thus its gelling capacity. © 2019 Society of Chemical Industry.

Combined Exercise and Leucine Supplementation Promotes Skeletal Muscle Protein Deposition in Tumor Bearing Mice

PURPOSE: To investigate the effect of concurrent exercise training and leucine supplementation on skeletal muscle protein deposition in Colon 26 tumor bearing mice. METHODS: Male BALB/c mice were divided into a control group (C, n=8), a C26 tumor bearing group (T, n=8) and a tumor bearing plus exercise and leucine supplementation group (TEL, n=8). Mice in the C and T groups were fed with normal chow diet, while mice in the TEL group were fed with formulated diet contained 5% leucine and received 30-min swimming training 3 days per week (Monday, Wednesday and Friday) and resistance training 3 days per week (Tuesday, Thursday and Saturday) for 2 weeks. At 24 hours after the last training session, blood and gastrocnemius muscle samples were collected under full anesthesia. The contents of TNF-α and IL-6 in gastrocnemius muscle and serum were determined by ELISA. maximal grip strength was measured with a commercial grip strength meter. Two-way ANOVAs and post-hoc tests were used for data analysis. RESULTS: After tumor bearing, cumulative food intake appeared to decrease, whereas body weight (20.7 g vs. 26.1 g), wet gastrocnemius muscle weight (97.3 mg vs. 128.9 mg), total protein content (35.7 mg/g vs. 51.2 mg/g), sarcoplasmic protein content (26.5 mg/g vs. 38.3 mg/g), myofibrillar protein content (28.6 mg/g vs. 43.3 mg/g) and muscle strength (82.7 g vs. 156.5 g) were significantly lower in the T group than in the C group (all p<0.01). TNF-α and IL-6 contents in serum and gastrocnemius were obviously higher in the T group than in the C group (p<0.01). After exercise and leucine supplementation, cumulative food intake and the TNF-α and IL-6 content were significantly lower in the TEL group than in the T group (p<0.05), while body weight (21.8 g), wet gastrocnemius muscle weight (111.1 mg), total protein content (40.3 mg/g), sarcoplasmic protein content (30.7 mg/g), myofibrillar protein content (34.0 mg/g) and muscle strength (112.2 g) were significantly higher in the TEL group than in the T group (p<0.05 to p<0.01). CONCLUSIONS: Combined exercise and leucine supplementation significantly ameliorated skeletal muscular protein deposition in C26 tumor bearing mice, which may be through down-regulating the inflammatory response. (Supported by Research Foundation of Sichuan Provincial Department of Education grant #18ZB0106).

Purification and biochemical characteristics of the extracellular protease from Pediococcus pentosaceus isolated from Harbin dry sausages

This study investigated the purification and biochemical characteristics of the protease produced by Pediococcus pentosaceus isolated from Harbin dry sausages. The optimized fermented conditions were as follows: fermentation time 36 h, initial pH 5 and fermentation temperature 30 °C. A 29.6 kDa extracellular protease was purified using ammonium sulphate deposition, ion exchange layer system and gel filtration. The protease produced by P. pentosaceus had a certain pH and thermal stability at pH 6 and 30 °C. The microbial protease activity could be inhibited by ethylene diamine tetraacetic acid disodium salt (EDTA). Vmax and Km of the protease were 43.9 mg/min and 8.3 mg/mL, respectively. Sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) reflected the ability of the protease to hydrolyse sarcoplasmic and myofibrillar proteins, particularly those of myosin heavy chain, paramyosin, actin, phosphorylase and creatine kinase-M types. 3D structure modelling of the P. pentosaceus protease found two domains in the protease protein and the correlation of the active sites with protease properties and substrate specificity. In conclusion, P. pentosaceus can be used as a starter culture or enzyme producing strain for inoculation in Harbin dry sausages.

Effects of Lactobacillus plantarum NJAU-01 on the protein oxidation of fermented sausage

This study was conducted to investigate the effects of Lactobacillus plantarum NJAU-01 isolated from Chinese dry-cured ham (Jinhua ham) on the regulation of protein oxidation of fermented sausages. Fermented sausages were prepared with different concentrations of L. plantarum NJAU-01 (105 CFU/g, 107 CFU/g and 109 CFU/g), and the commercial strain was used as positive control. The results showed that L. plantarum NJAU-01 at 107 CFU/g and 109 CFU/g significantly lowered the protein carbonyl content and protein surface hydrophobicity compared with the control (P < 0.05). The total sulfhydryl contents in L. plantarum NJAU-01 groups were significantly higher than that of the group without starter culture (P < 0.05). Significant changes were found in sarcoplasmic protein bands within 130–250 kDa, 100–130 kDa and 25–35 kDa during sausage fermentation (P < 0.05). Our data suggest that L. plantarum NJAU-01 has the potential to be an antioxidant starter culture in fermented sausages.

Effect of protein thermal stability and protein secondary structure on the roasted mutton texture and colour from different cuts

The age and cut of mutton are important factors influencing the suitability of roasting. In this study, the sensory quality, texture profile and surface colour of roasted mutton cuts (back strap, silverside, square cut shoulder, breast and flap and oyster cut) from Merino sheep slaughtered at ages of six months and two years were investigated. Also the protein thermal stability and protein secondary structure of different samples were also evaluated. The results showed that the muscles of back strap, silverside and oyster cut were much more suitable for roasting, presented higher sensory scores and better corresponding instrumental colour, texture properties and shear force. Lower protein thermal stability of collagen, sarcoplasmic proteins and actin in raw muscle might be the cause of the higher values of sensory attributes, L⁎, texture profiles and lower a⁎ value of roasted mutton. The lower relative percentage of protein α-helix in fresh mutton might contribute to the higher protein random coil of roasted mutton, and these contribute with a great texture and colour. It concludes that differential protein thermal stability and protein secondary structure of muscles partially affect the roast quality of lamb.

Mapping changes in sarcoplasmatic and myofibrillar proteins in boiled pork using hyperspectral imaging with spectral processing methods

Hyperspectral imaging technology was investigated to examine the changes of sarcoplasmatic and myofibrillar proteins contents in boiled pork. Different spectral pre-processing methods were employed to improve the partial least squares regression (PLSR) models. Seven optimal wavelengths in the region of 400–2000 nm without spectral pre-processing were used to build the best PLSR model for predicting the sarcoplasmatic proteins contents with R2p of 0.9185 and RMSEP of 2.50 mg/g. Based on multiplicative scatter correction (MSC) method, eight wavelengths in the region of 400–1000 nm were also selected to construct the best predictive PLSR model for myofibrillar protein contents with R2p of 0.9161 and RMSEP of 2.71 mg/g. The changes in sarcoplasmatic and myofibrillar proteins contents of boiled pork during different cooking periods were successfully visualized.

Purification and biochemical characteristics of the microbial extracellular protease from Lactobacillus curvatus isolated from Harbin dry sausages

This study investigates the purification and biochemical characteristics of the protease secreted by Lactobacillus curvatus R5, which was isolated from Harbin dry sausages. The optimized fermentation conditions were fermentation time 36 h, initial pH 6 and fermentation temperature 37 °C. An extracellular protease was purified using ammonium sulfate precipitation, ion-exchange layer and gel filtration. Sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis showed that molecular weight of the purified protease was 45.3 kDa. Protease produced by L. curvatus R5 reached a higher relative protease activity at pH 6, 40 °C, and the purified protease exhibited pH and thermal stability at pH 6 and 40 °C. The microbial protease activity can be inhibited by ethylene diamine tetraacetic acid disodium salt (EDTA). The Vmax and Km of the protease were 53 mg/min and 15.9 mg/mL, respectively. SDS-PAGE reflects the ability of the protease to hydrolyse myofibrillar protein and sarcoplasmic protein, especially on myosin heavy chain, actin, myosin light chain and phosphorylase. The 3D structure and the Ramachandran plot of L. curvatus R5 protease was obtained by homology modelling. The Ramachandran plot analysis revealed that the purified protease was composed of 366 amino acids, and its residues in favoured, allowed, generously allowed and disallowed regions were 84.6%, 11.3%, 3.2% and 0.9% residues, respectively. Molecular docking showed that the substrate actin bound to the protease active site by hydrogen bonding and hydrophobic interaction. This research provides a basis for understanding the enzymatic properties of L. curvatus R5 protease. In conclusion, L. curvatus R5 can be used as a starter culture or protease-producing strain to inoculate Harbin dry sausages.

Evaluating the effect of protein modifications and water distribution on bitterness and adhesiveness of Jinhua ham

Defects with textures and flavors are a common problem, causing many economic losses in the dry-cured ham industry. To obtain a better understanding of the defects of dry-cured ham, texture, protein denaturation, protein structure, and water distribution of normal and defective hams were investigated. Compared with normal ham, more than 1.5-fold values in adhesiveness and bitterness, and less than 0.8-fold values in hardness were found in defective ham. The intense denaturation of sarcoplasmic proteins and actin, and the dramatic transformation of α-helix to β-sheet were the key modification of proteins; a high proportion (92.39%) of immobile water contributed to the excessive softness and adhesiveness of defective hams. Furthermore, high denaturation of proteins could accelerate the degradation of proteins, which further developed the bitterness and adhesiveness of defective hams. Partial least squares regression demonstrated that the discrepancies in protein denaturation, protein structure and water distribution were related with bitterness and adhesiveness of Jinhua ham.

Nexilin Is a New Component of Junctional Membrane Complexes Required for Cardiac T-Tubule Formation.

Membrane contact sites are fundamental for transmission and translation of signals in multicellular organisms. The junctional membrane complexes in the cardiac dyads, where transverse (T) tubules are juxtaposed to the sarcoplasmic reticulum, are a prime example. T-tubule uncoupling and remodeling are well-known features of cardiac disease and heart failure. Even subtle alterations in the association between T-tubules and the junctional sarcoplasmic reticulum can cause serious cardiac disorders. NEXN (nexilin) has been identified as an actin-binding protein, and multiple mutations in the NEXN gene are associated with cardiac diseases, but the precise role of NEXN in heart function and disease is still unknown. Nexn global and cardiomyocyte-specific knockout mice were generated. Comprehensive phenotypic and RNA sequencing and mass spectrometry analyses were performed. Heart tissue samples and isolated single cardiomyocytes were analyzed by electron and confocal microscopy. Global and cardiomyocyte-specific loss of Nexn in mice resulted in a rapidly progressive dilated cardiomyopathy. In vivo and in vitro analyses revealed that NEXN interacted with junctional sarcoplasmic reticulum proteins, was essential for optimal calcium transients, and was required for initiation of T-tubule invagination and formation. These results demonstrated that NEXN is a pivotal component of the junctional membrane complex and is required for initiation and formation of T-tubules, thus providing insight into mechanisms underlying cardiomyopathy in patients with mutations in NEXN.

Effect of Different Storage-Temperature Combinations on Longissimus dorsi Quality upon Sous-vide Processing of Frozen/Thawed Pork.

This study investigated the effect of storage state (chilled state on sous-vide, CS; frozen state without thawing on sous-vide, FS; and frozen/thawed states on sous-vide, TS) and sous-vide cooking temperature (65°C and 72°C) on the longissimus dorsi muscle quality of pork. FS showed a higher moisture content than that of CS and TS (p<0.001), whereas both FS and CS showed higher expressible moisture loss than that of TS (p<0.001). FS showed a lower cooking loss (p<0.001) than that of CS and TS. FS and TS exhibited significantly higher lipid oxidation than that of CS. Carbonyl and sulfhydryl content were not significantly affected by the storage treatment. FS and TS exhibited lower shear force than that of CS (p<0.001). FS and TS showed higher springiness than that of CS (p<0.001), FS exhibited lower gumminess than that of CS and TS (p<0.01). Sous-vide treatment at 65°C exhibited significantly higher moisture content and lower expressible moisture loss, cooking loss, and total and sarcoplasmic protein than those at 72°C. Shear force and springiness of 65°C-treated groups were lower than those of 72°C-treated groups (p<0.01). Cooking temperature significantly influenced overall acceptability, whereas the storage state did not affect the overall acceptability. These results indicated that meat quality might be improved upon cooking from the frozen or frozen/thawed state using sous-vide when compared with traditional processing.

How can heat stress affect chicken meat quality? - a review.

Heat stress is one of the most important environmental stressors for the poultry industry in the world. Reduced growth rate, low feed efficiency, impaired immunological responses, changes in intestinal microflora, and deterioration of meat quality are the consequences of acute or chronic heat stress. In terms of meat quality, 3 primary mechanisms have been suggested to explain this phenomenon: 1) rapid drop in pH during and after slaughter due to the glycogen conversion to increase in lactic acid accumulation especially when the muscle temperature is high, a combination of high temperature and low pH that facilitates the denaturation of sarcoplasmic proteins resulting in lower water-holding capacity of muscle; 2) acceleration of panting to dissipate body heat, which increases CO2 exhalation and pH drop in blood, initiates metabolic acidosis in skeletal muscle. Increase in panting is also associated with a high release of corticosteroid hormones; 3) the reactive oxygen species produced by heat stress increases the oxidative stress in the birds, which can damage the structure and functions of the enzymes that regulate sarcoplasmic calcium levels in muscles. Overall, these changes in the muscle cells accentuate energy expenditure due to constant muscle contractions. This review discusses the scientific evidence about how heat stress affects the quality of chicken meat through the acid/base status, oxidative reactions, and changes in hormonal secretions.