351 research outputs found

    Mitochondrial functionality and beef colour: A review of recent research

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    The bright-red colour of meat that consumers prefer depends on the depth of oxygen diffusion into the tissue and myoglobin oxygenation. Interestingly, both processes are influenced by mitochondrial activity in postmortem muscle. The transition of muscle metabolism from aerobic to anaerobic pathways affects various cellular processes including mitochondrial functionality. Numerous studies report that even with compromised structure, mitochondria continue to influence postmortem beef colour via oxygen consumption and metmyoglobin reducing activity. Hence, an in-depth understanding of the pre- and post-harvest factors affecting mitochondrial functionality can significantly enhance existing knowledge of meat colour and colour stability. Several comprehensive reviews have discussed the biochemical factors affecting meat colour, but there are only a few that have sections on the impact of mitochondria on beef colour. Furthermore, advancement of high-throughput techniques such as metabolomics and proteomics has enabled researchers to elucidate metabolite and protein changes related to mitochondria. Therefore, the objective of this review is to provide an overview on the role of mitochondria in beef colour, with a focus on recent advances in mitochondrial research, oxygen consumption, and metmyoglobin reducing ability.Keywords: Myoglobin, metmyoglobin reducing activity, meat colour, metabolomics, oxygen consumption, proteomic

    Intramuscular variation in mitochondrial functionality of beef semimembranosus

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    Intramuscular color stability variations in beef semimembranosus have been reported previously. Mitochondria remain biochemically active in postmortem muscle and can influence fresh beef color stability. However, the role of mitochondrial functionality in intramuscular color variations in beef semimembranosus is yet to be examined. We examined the functionality of mitochondria isolated from outside (OSM) and inside (ISM) regions of beef semimembranosus. Semimembranosus muscles (n = 5) were collected from inside rounds of beef carcasses 48 h post-mortem and were separated to OSM and ISM steaks. Color attributes were evaluated instrumentally and biochemically on days 0 and 4 of retail display, whereas mitochondrial oxygen consumption rate (OCR) was measured on day 0 using succinate as substrate using steaks frozen during fabrication. Mitochondrial OCR was significantly greater in OSM than in ISM on day 0. The ISM steaks exhibited significantly greater redness (a* value) than OSM steaks on day 0, but OSM steaks had significantly greater redness than the ISM counterparts on day 4. During retail display, ISM steaks exhibited greater lightness (L* value) than OSM steaks. However, OSM demonstrated significantly greater color stability and metmyoglobin reducing activity than ISM throughout the display. The observed differences in mitochondrial OCR between ISM and OSM steaks indicated that mitochondrial biochemistry possibly contributes to the intramuscular color variations in beef semimembranosus.Keywords: Beef color, color stability, mitochondria, semimembranosu

    Ractopamine-induced changes in sarcoplasmic proteome profile of post-rigor pork semimembranosus muscle

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    Ractopamine is a beta-adrenergic agonist that increases leanness and carcass weight in finishing pigs. Our previous study observed that dietary ractopamine increased the abundance of several glycolytic enzymes in the sarcoplasmic proteome of post-rigor pork longissimus thoracis muscle. Pork semimembranosus is an economically important muscle and demonstrates differences in biochemistry compared with longissimus thoracis. Nonetheless, the effects of ractopamine on sarcoplasmic proteome of semimembranosus have not been evaluated yet. Therefore, this study examined the influence of ractopamine on sarcoplasmic proteome of post-rigor pork semimembranosus. Analyses of sarcoplasmic proteome of semimembranosus muscles from control (CON; diet without ractopamine) and ractopamine-fed (RAC; 7.4 mg/kg for 14 days followed by 10.0 mg/kg for 14 days) barrows revealed that haemoglobin subunit beta, alpha-crystallin B, and titin fragments were over-abundant in CON. In contrast, myosin light chain 1/3 and tripartite motif-containing protein 72 were over-abundant in RAC. The low abundance of haemoglobin subunit beta and alpha crystallin B in RAC could be attributed to fibre type shift (from oxidative to glycolytic) in response to ractopamine. The over-abundance of MLC 1/3 and tripartite motif-containing protein 72 in RAC could be due to the increased myofibrillar protein synthesis and muscle mass in ractopamine-fed pigs. Dietary ractopamine decreased the abundance of sarcoplasmic proteins involved in oxygen transport and chaperone activity, but increased the abundance of proteins involved in muscle contraction and plasma membrane repair in pork semimembranosus muscle.Keywords: Pork, ractopamine, sarcoplasmic proteome, semimembranosu

    Hard Thermal Loops, Gauged WZNW Action and the Energy of Hot Quark-Gluon Plasma

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    The generating functional for hard thermal loops in QCD is rewritten in terms of a gauged WZNW action by introducing an auxiliary field. This shows in a simple way that the contribution of hard thermal loops to the energy of the quark-gluon plasma is positive.Comment: 9 pages, CU-TP 60

    Supranutritional supplementation of vitamin E influences mitochondrial proteome profile of post-mortem longissimus lumborum from feedlot heifers

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    Supplementation of vitamin E improves beef colour stability by minimizing lipid oxidation-induced myoglobin oxidation. Mitochondria affect myoglobin redox stability, and dietary vitamin E influences mitochondrial functionality in skeletal muscles. Nonetheless, the influence of vitamin E on the mitochondrial proteome of beef skeletal muscles has yet to be  investigated. Therefore, the objective of this study was to examine the effect of dietary vitamin E on mitochondrial proteome of post-mortem beef longissimus lumborum (LL) muscle. Beef LL muscle samples (24 hours post-mortem) were obtained from the carcasses of nine (n = 9) vitamin E-fed (VITE) (1000 IU vitamin E for 89 days) and nine (n = 9) control (CONT) (diet without supplemental vitamin E) heifers. The mitochondrial proteome was analysed using two-dimensional gel electrophoresis and mass spectrometry, and nine differentially abundant spots were identified. All the differentially abundant spots were over-abundant in CONT, and the proteins were electron transport chain enzymes (NADH dehydrogenase iron-sulphur protein 8, NADH dehydrogenase flavoprotein 2, and cytochrome c oxidase subunit 5B), metabolic enzymes (succinate-CoA ligase (ADP-forming) subunit beta; dihydrolipoyllysine-residue succinyltransferase component of 2-oxoglutarate dehydrogenase complex; pyruvate dehydrogenase protein X component), and enzymes involved in ATP regeneration (creatine kinase S-type). The low abundance of these proteins in VITE may decrease mitochondrial activity, resulting in low oxidative activity. These findings suggest that the strong antioxidant activity of vitamin E leads to less expression of mitochondrial oxidative enzymes in beef skeletal muscles.Keywords: Beef colour, lipid oxidation, mitochondrial enzyme

    Ractopamine-induced changes in the proteome of post-mortem beef longissimus lumborum muscle

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    Ractopamine is a beta-adrenergic agonist that is approved for use in beef cattle, pigs and turkeys as a repartitioning agent to increase lean muscle deposition and decrease lipogenesis. Although the effects of dietary ractopamine on the proteome profile of post-mortem pork muscles have been examined, its influence on beef muscle proteome has not been studied. Therefore, the objective of this study was to examine the effect of ractopamine on the proteome profile of post-mortem beef longissimus lumborum (LL) muscle. LL muscle samples were obtained from the carcasses of six (n = 6) steers fed ractopamine (RAC; 400 mg ractopamine hydrochloride for 28 days) and six (n = 6) steers fed no ractopamine (CON). The muscle proteome was analysed using two-dimensional gel electrophoresis and tandem mass spectrometry. Five differentially abundant spots were identified, and all the spots were over-abundant in RAC. The identified proteins were involved in muscle structure development (F-actin-capping protein subunit beta-2; PDZ and LIM domain protein-3), chaperone activity (heat shock protein beta-1), oxygen transport (myoglobin), and glycolysis (L-lactate dehydrogenase A chain). These results suggested that dietary ractopamine could influence the abundance of enzymes associated with muscle development and muscle fibre type shift in beef LL muscle.Keywords: growth promotants, meat quality, proteomic

    Flecainide challenge test: Predictors of unmasking of type 1 Brugada ECG pattern among those with non-type 1 Brugada ECG pattern

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    AbstractBackgroundMany subjects in community have non-type 1 Brugada pattern ECG with atypical symptoms, relevance of which is not clear. Provocative tests to unmask type 1 Brugada pattern in these patients would help in diagnosing Brugada Syndrome. However sensitivity and specificity of provocating drugs are variable.MethodsWe studied 29 patients referred to our institute with clinical presentation suggestive but not diagnostic of Brugada or with non-Type 1 Brugada pattern ECG. Flecainide Challenge Test (FCT) was done in these patients (IV Flecainide test in 4 patients and Oral Flecainide in 25 patients). Resting 12-lead ECG with standard precordial leads and ECG with precordial leads placed 1 Intercostal space above were performed after flecainide administration every 5 min for first 30 min and every 30 min thereafter until ECG became normal or upto 6 h. The positivity was defined as inducible Type 1 Brugada pattern in atleast 2 right sided leads.ResultMedian age was 35(range = 5–65) years. In 16 (55%) patients the Type 1 Brugada pattern was unmasked. There were no episodes of major AV block, atrial or ventricular tachyarrhythmia. Three groups were considered for analysis: Group 1(n = 9) – FCT Positive among patients with non-type 1 Brugada ECG pattern, Group 2(n = 4) – FCT Negative among the patients with non-type 1 Brugada ECG pattern, and Group 3(n = 7) – FCT Positive among patients with no spontaneous Brugada ECG pattern. Binary logistic regression analysis found that family h/o SCD was predictive of FCT positivity in Group 1 (Odd’s ratio 21, 95% Confidence interval 1.04 to 698.83, p = 0.004).ConclusionOral flecainide is useful and safe for unmasking of Type I Brugada pattern. In our study, among the many variables studied, family history of sudden cardiac death was the only predictor of flecainide test positivity among those with non-Type 1 Brugada pattern

    Absence seizures as resetting mechanisms of brain dynamics

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    To understand the increase in age-related incidence and frequency of absence seizures in the rat brain, we investigated the effect of these seizures on brain dynamics. This paper puts forward the hypothesis that age-related differences in the expression of absence seizures are associated with the ability of the seizures to reset brain dynamics

    Manifest covariance and the Hamiltonian approach to mass gap in (2+1)-dimensional Yang-Mills theory

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    In earlier work we have given a Hamiltonian analysis of Yang-Mills theory in (2+1) dimensions showing how a mass gap could arise. In this paper, generalizing and covariantizing from the mass term in the Hamiltonian analysis, we obtain two manifestly covariant and gauge-invariant mass terms which can be used in a resummation of standard perturbation theory to study properties of the mass gap.Comment: Sections 1, 4 modified, part of section 2 moved to appendix, 19 pages, LaTe
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