Species dependence of fish myosin stability to heat and frozen storage

The thermal stabilities of the proteins of a range of fish muscles of different habitat temperatures were determined by differential scanning calorimetry before and after frozen storage at 20°C.
In whole muscle a clear relationship was seen between habitat temperature and the thermal denaturation of myosin, which persisted when isolated myosins were analysed under conditions close to physiological pH and ionic strength. the ionic environment of the myosin molecules in the whole tissue will, however, not be exactly the same as in the myosin solution.
No significant correlations were seen between habitat temperature, ultimate pH and other analytical parameters.
After frozen storage, the myosin transitions in red snapper, a warm water species, was markedly changed in whole muscle but not in isolated myosin, suggesting the post mortem development of an interaction with other muscle proteins. In contrast, in cod, a cold water species, changes in myosin transitions were very similar, both in whole muscle and isolated myosin.
The implications of species differences in the 'melting' of myosin domains and changes in textural quality during frozen storage are discussed briefly.     

Capillary Zone Electrophoresis of Fish Muscle Sarcoplasmic Proteins

A capillary zone electrophoresis (CZE) method for rapid separation of fish muscle sarcoplasmic proteins (SAJR) was developed using a highionic-strength phosphate buffer and an untreated, fused silica capillary (20 μm i.d. X 20 cm). Changes in pH between 6.6-7.5 resulted in differences in mobility, separation factors, and number of SAR moieties. An optimal SAR profile was obtained at pH 7.4. When used to monitor frozen storage changes in SAR from cod (Atlantic, Ling, Pacific) and pollock fillets, the procedure indicated both species differences and low-and high- molecular-weight frozen storage changes. CZE is an effective screening/quantification alternative to conventional electrophoresis and/ or HPLC because it is fast (<10 min), simple, sensitive, precise, and readily automated.     

Toxic and essential metals in liver, kidney and muscle of pigs at slaughter in Galicia, north-west Spain

The aims of the study were to evaluate toxic and essential metal concentrations in meat and offal from pigs in north-west Spain to compare these with reported metal concentrations in pigs in other countries and in cattle in this region, and to relate the observed concentrations to maximum acceptable concentrations. Samples from 63 pigs aged 6 months were randomly collected at slaughter. After acid digestion, levels of metals were determined by ICP-OES and ICP-MS. As regards the toxic metals, mean concentrations in liver, kidney and muscle were 0.073, 0.308 and 0.009 mg kg^-1 fresh weight for cadmium, 0.004, 0.008 and 0.003 mg kg^-1 for lead, 0.013, 0.011 and 0.003 mg kg^-1 for arsenic, and 0.001, 0.002 and 0.001 mg kg^-1 for mercury. These concentrations can be considered low, and in general similar to those reported in similar studies in recent years. In addition, maximum admissible concentrations established by the European Union were not exceeded in any sample. As regards the essential metals, concentrations in liver, kidney and muscle were 14.9, 5.63 and 6.85 mg kg^-1 for copper, 81.3, 28.9 and 42.5 mg kg^-1 for zinc, 195, 51.6 and 26.5 mg kg^-1 for iron; 1.17, 2.51 and 0.656 mg kg^-1 for selenium, 3.32, 1.56 and 1.01 mg kg^-1 for manganese, 0.023, 0.027 and 0.003 mg kg^-1 for cobalt, 0.120, 0.077 and 0.131 mg kg^-1 for chromium, 0.009, 0.027 and 0.026 mg kg^-1 for nickel, and 1.62, 0.683 and 0.140 mg kg^-1 for molybdenum. These concentrations are all within the accepted adequate-safe ranges for this animal species, and in general are in line with those previously reported in the literature.     

Relationship between rate of post mortem pH fall and ageing of Longissimus muscle in pietrain pigs

Twenty-six pietrain pigs exhibiting wide variability in pH₄₅ (pH value 45 min post mortem) values were used to assess the mechanical behaviour of cooked and raw Longissimus muscle at 24 h and 8 days post mortem. Rheological behaviour was studied in compression under strain conditions which allow specific determination of myofibrillar resistance. The muscles were divided into three groups on the basis of pH₄₅ values: (Severe pale, soft and exudative (PSE), pH₄₅ = 5.49 ± 0.03 (n = 9); PSE pH₄₅ = 5.78 ± 0.04 (n = 10); Normal, pH₄₅ = 6.35 ± 0.05 (n = 7). The three groups did not differ significantly for ultimate pH (pH_u = 5.57 ± 0.02 for the 26 muscles). A lower mechanical resistance of raw samples was found in the Normal group, regardless of the time post mortem. Although this difference was not significant, a significant relationship was found between this trait and pH₄₅ at both times post mortem (r = ?0.43, P < 0.05, at 24 h and r = ?0.44, P < 0.05, at 8 days post mortem). However, no significant effect of pH₄₅ was found on the mechanical resistance of cooked muscles. The relative decrease in myofibrillar strength after an 8-day ageing period was not affected by pH₄₅ but this was due to the fact that the three groups exhibited different starting points. Mechanical resistance of raw and cooked muscles at 24 h post mortem were significantly related to pH_u (r = ?0.55, P < 0.01, and r = ?0.49, P < 0.05, respectively). The present results show that after an 8-day ageing period, PSE muscles are not fully aged.     

A methodology for muscular isometric endurance and fatigue research

The objective of this study was to develop a reliable statistical method of finding a cut-off point between the endurance section and the fatigue section from a single endurance-fatigue curve of force versus time for extended times. Two age groups (20–29, 50–59 years old) with 10 subjects in each group participated in this study. Two muscle groups (biceps and quadriceps) were tested at five levels of % MVC (20, 40, 60, 80 and 100 % MVC). Subjects were instructed to exert a force and reach a designated % MVC level and maintain that level for as long as possible until asked by the experimenter to stop. Each condition was tested for five minutes. The method developed used the sum of squares technique to find the optimal cut-off point on the curve thus, determining the endurance time. The methodology proved to be useful and reliable. The steps involved along with an example are discussed.     

A review of joint and muscle load simulation relevant to in-vitro stress analysis of the hip

Model analysis of the hip has become an important research technique in the assessment of implant performance in Total Hip Replacements (T.H.R.). In the literature to date, however, there is an absence of suitable criteria to aid in the selection of representative joint and muscle loading conditions relevant to such analyses. Consequently, the interpretation of information regarding the loading of the hip joint varies greatly between studies. The objective of this study, therefore, is to review the procedures used to establish these forces and to outline how they may be appliedto in-vitro modeltesting of the proximal femur and the pelvis. The muscles active at the hip joint are categorised with respect to their positions and primary actions. The magnitudes of the muscle and joint loads, as estimated by force determination studies employing in-vitro, in-vivo and mathematical modelling techniques, are reviewed. Applications illustrating the load simulations applied to the model analysis of an implanted Exeter femoral prosthesis and the in-vitro testing of cementless acetabular cups are also presented. While there is reliable information regarding the joint reaction between the femur and the acetabulum, it is difficult to represent accurately the muscular loading, due to the conflicting information presented in the literature. It is possible, however, to apply this information to load simulations in a limited manner in an attempt to predict trends in behaviour which are representative of the in-vivo situation.     

Quantitative high-resolution13C and1H nuclear magnetic resonance of ω3 fatty acids from white muscle of atlantic salmon (Salmo salar)

High-resolution¹³C nuclear magnetic resonance (NMR) spectra have been obtained and used to define the ω3 (n-3) fatty acid distribution in lipid extract and white muscle from Atlantic salmon (Salmo salar). The¹³C spectrum of lipid extracted from muscle gives quantitative information about the individual n-3 fatty acids, 18:2n-6, 20:1/22:1 and groups of fatty acids. The quantitative data compare favorably with those obtained by gas-liquid chromatography. The¹H NMR spectrum of the lipid extract gives information about the amount of 22:6n-3 and the total content of n-3 fatty acids. The¹³C NMR technique also revealed the positional distribution (1,3- and 2-acyl) of the important 20:5n-3 and 22:6n-3 acids in the triacylglycerol molecules. In the quantitative¹³C NMR spectrum of white muscle, the methyl region of the acyl chains of triacylglycerols gave rise to sufficiently resolved signals to permit estimation of the total concentration of lipids and the n-3 fatty acid content. The NMR data are in good agreement with corresponding data obtained by traditional methods.     

MAPKs Are Highly Abundant but Do Not Contribute to α1-Adrenergic Contraction of Rat Saphenous Arteries in the Early Postnatal Period

Previously, the abundance of p42/44 and p38 MAPK proteins had been shown to be higher in arteries of 1- to 2-week-old compared to 2- to 3-month-old rats. However, the role of MAPKs in vascular tone regulation in early ontogenesis remains largely unexplored. We tested the hypothesis that the contribution of p42/44 and p38 MAPKs to the contraction of peripheral arteries is higher in the early postnatal period compared to adulthood. Saphenous arteries of 1- to 2-week-old and 2- to 3-month-old rats were studied using wire myography and western blotting. The α₁-adrenoceptor agonist methoxamine did not increase the phosphorylation level of p38 MAPK in either 1- to 2-week-old or 2- to 3-month-old rats. Accordingly, inhibition of p38 MAPK did not affect arterial contraction to methoxamine in either age group. Methoxamine increased the phosphorylation level of p42/44 MAPKs in arteries of 2- to 3-month-old and of p44 MAPK in 1- to 2-week-old rats. Inhibition of p42/44 MAPKs reduced methoxamine-induced contractions in arteries of 2- to 3-month-old, but not 1- to 2-week-old rats. Thus, despite a high abundance in arterial tissue, p38 and p42/44 MAPKs do not regulate contraction of the saphenous artery in the early postnatal period. However, p42/44 MAPK activity contributes to arterial contractions in adult rats.     

Effect of pH on the formation of edible films made from the muscle proteins of Blue marlin (Makaira mazara)

Whole meat of Blue marlin (Makaira mazara) was used to prepare edible films. Protein solubility in film-forming solutions was high at acidic and alkaline pHs, while that at neutral pH was close to zero. Acidic and alkaline pHs improved the tensile strength while the effects of pH, on elongation at break, water vapour permeability and light transmission of the films, were not significant. From the film solubility in various protein denaturants it was revealed that the main interaction responsible for the formation of acidic and alkaline pH films was hydrophobic interaction, while that for neutral pH films was ionic bonding.     

Striated Preferentially Expressed Protein Kinase (SPEG) in Muscle Development,Function, and Disease

Mutations in striated preferentially expressed protein kinase (SPEG), a member of the myosin light chain kinase protein family, are associated with centronuclear myopathy (CNM), cardiomyopathy, or a combination of both. Burgeoning evidence suggests that SPEG plays critical roles in the development, maintenance, and function of skeletal and cardiac muscles. Here we review the genotype-phenotype relationships and the molecular mechanisms of SPEG-related diseases. This review will focus on the progress made toward characterizing SPEG and its interacting partners, and its multifaceted functions in muscle regeneration, triad development and maintenance, and excitation-contraction coupling. We will also discuss future directions that are yet to be investigated including understanding of its tissue-specific roles, finding additional interacting proteins and their relationships. Understanding the basic mechanisms by which SPEG regulates muscle development and function will provide critical insights into these essential processes and help identify therapeutic targets in SPEG-related disorders.