Are muscle fiber types different between normal and dark-cutting beef?

Muscle fiber (MF) characteristics of Longissimus thoracis (LT) muscles from heifer (n = 11) and steer (n = 12) carcasses graded Canada AA (AA, normal, n = 4/sex) or dark-cutting (Canada B4) were examined and related to beef quality. Atypical (AB4, pH < 5.9, n = 4/sex) and typical (TB4, pH > 5.9, n = 3 and 4 for heifers and steers, respectively) dark-cutting carcasses were represented. Muscle fiber type proportions did not differ between AA, AB4 and TB4 muscles, although type I and IIB muscle fiber diameters were greater in TB4 than in AA LT. That AB4 muscle fiber proportions were not different from AA and TB4 muscles suggests that the increased MF diameter of TB4 muscle was due to water retained by muscle proteins at high ultimate pH, as evidenced by decreased cooking loss. Dark-cutting was therefore unrelated to muscle fiber proportions, and increased Type I and IIB diameters in dark cutting LT were likely driven by elevated intramuscular ultimate pH.

Studying Chemical Composition of Myofibril and Sarcoplasmic Proteins Separated From Different Types of Meats

The present study was dealt with the estimation of the chemical composition (moisture, protein, fat, and ash) and physical properties (pH and water holding capacity) of camel, duck, and tuna meat purchased from local markets. Muscle proteins were separated, including myofibril and sarcoplasmic proteins from these meats, estimation of the yield and study of their content. have been studied. the results were as follows: 1. Statistical results disclosed that there was a significant difference at a probability level (P≤0.05) in the percentage of moisture, protein, fat, ash, pH, and values of water holding capability in each of camel, duck, and tuna's meat. 2. Statistical results made a clear reference that there were significant differences at a probability level (P≤0.05) in the percentage of yield, moisture, protein, fat, and ash of myofibril and sarcoplasmic proteins in each of camel, duck, and tuna's meat. Also, a dual interference between meat type and protein type was significant in its impact on percentages of yield and chemical composition. 3. It was observed the percentage of moisture and fat in tuna meat was higher than the percentage of moisture in duck meat. As to the lowest percentage of moisture, it was in the meat of tuna, while the tuna meat recorded the highest percentage in protein and ash, then followed by the percentage of protein and ash in duck meat, while camel's meat recorded the lowest percentage of protein and ash. Besides, results indicated that the values of pH and water holding capability of duck meat were higher than that in the meat of tuna meat and camel. 4. It was found that the percentage of the yield for proteins of a myofibril of duck meat was higher than that in the meat of tuna and camels, as the percentage of yield of sarcoplasmic proteins for tuna was higher than that in the meat of duck and camels. 5. It was found that the percentage of yield for myofibril of duck meat was higher than that in the meat of tuna and camels. As to the percentage of yield for sarcoplasmic proteins of tuna meat, it was higher than that in the meat of duck and camels. 6. The highest percentage of moisture for myofibril proteins was in the meat of camels, and the lowest percentage of it was registered in myofibril proteins in tuna meat, whilst the highest percentage of moisture for sarcoplasmic proteins was registered in the meat of duck, and the lowest of it registered in sarcoplasmic proteins in tuna meat. 7. It was observed that the highest percentage of protein and fat for myofibril and sarcoplasmic proteins was registered in tuna meat, as the lowest percentage of protein and fat for myofibril and sarcoplasmic proteins were observed in duck meat. 8. The study came up with a result revealing that the percentage of ash in proteins of myofibril proteins for duck meat was higher than that in myofibril proteins for camels and tuna meat, whilst, the percentage of ash in sarcoplasmic proteins for camel meat was higher than that in sarcoplasmic proteins for duck and tuna meat. 9. Results showed that the highest concentration of sarcoplasmic proteins was in tuna meat, followed by duck meat, and the lowest concentration for these proteins was in camel meat. The values of proteins (myosin, tropomyosin, reticulin, and collagen) in camel meat, then followed by duck meat, whilst the lowest values for these proteins were in tuna meat.

Thermal Pain Thresholds Are Significantly Associated with Plasma Proteins of the Immune System in Chronic Widespread Pain—An Exploratory Pilot Study Using Multivariate and Network Analyses

Chronic widespread pain (CWP), including fibromyalgia (FM), is characterized by generalized musculoskeletal pain. An important clinical feature is widespread increased pain sensitivity such as lowered pain thresholds for different stimuli such as heat (HPT) and cold (CPT). There is a growing interest in investigating the activated neurobiological mechanisms in CWP. This explorative proteomic study investigates the multivariate correlation pattern between plasma and muscle proteins and thermal pain thresholds in CWP and in healthy controls (CON). In addition, we analysed whether the important proteins and their networks for CPT and HPT differed between CWP and CON. We used a proteomic approach and analysed plasma and muscle proteins from women with CWP (n = 15) and CON (n = 23). The associations between the proteins and CPT/HPT were analysed using orthogonal partial least square (OPLS). The protein–protein association networks for the important proteins for the two thermal pain thresholds were analysed using STRING database. CWP had lowered pain thresholds for thermal stimulus. These levels were generally not related to the included clinical variables except in CWP for HPT. Highly interacting proteins mainly from plasma showed strong significant associations with CPT and HPT both in CWP and in CON. Marked differences in the important proteins for the two thermal pain thresholds were noted between CWP and CON; more complex patterns emerged in CWP. The important proteins were part of the immune system (acute phase proteins, complement factors, and immunoglobulin factors) or known to interact with the immune system. As expected, CWP had lowered pain thresholds for thermal stimulus. Although different proteins were important in the two groups, there were similarities. For example, proteins related to the host defence/immunity such as acute phase proteins, complement factors, immunoglobulin factors, and cytokines/chemokines (although not in CON for CPT) were important habitual/tonic factors for thermal pain thresholds. The fact that peripheral proteins contribute to thermal pain thresholds does not exclude that central factors also contribute and that complex interactions between peripheral and central factors determine the registered pain thresholds in CWP.

Exploring Obscurin and SPEG Kinase Biology

Three members of the obscurin protein family that contain tandem kinase domains with important signaling functions for cardiac and striated muscles are the giant protein obscurin, its obscurin-associated kinase splice isoform, and the striated muscle enriched protein kinase (SPEG). While there is increasing evidence for the specific roles that each individual kinase domain plays in cross-striated muscles, their biology and regulation remains enigmatic. Our present study focuses on kinase domain 1 and the adjacent low sequence complexity inter-kinase domain linker in obscurin and SPEG. Using Phos-tag gels, we show that the linker in obscurin contains several phosphorylation sites, while the same region in SPEG remained unphosphorylated. Our homology modeling, mutational analysis and molecular docking demonstrate that kinase 1 in obscurin harbors all key amino acids important for its catalytic function and that actions of this domain result in autophosphorylation of the protein. Our bioinformatics analyses also assign a list of putative substrates for kinase domain 1 in obscurin and SPEG, based on the known and our newly proposed phosphorylation sites in muscle proteins, including obscurin itself.