Slow Skeletal Myosin Heavy Chain Research Articles

Effects of Dietary L-malic Acid Supplementation on Meat Quality, Antioxidant Capacity and Muscle Fiber Characteristics of Finishing Pigs.

L-malic acid is a vital intermediate in the citric acid cycle and has been reported to improve the antioxidant capacity and aerobic oxidation of weaned piglets; however, its application in finishing pigs is limited at present. This study explored the effects of dietary L-malic acid supplementation on the carcass traits and meat quality of finishing pigs. In a 45-day experiment, 192 Duroc × Landrace × Yorkshire pigs (75.01 ± 0.51 kg) were divided into four treatments, i.e., a basal diet supplemented with 0, 0.5%, 1%, and 2% L-malic acid complex. The results showed that L-malic acid supplementation had no effects on the growth performance of finishing pigs. Importantly, L-malic acid significantly increased redness (a*) value at 24-h postmortem (quadratic, p < 0.05) and tended to increase the proportion of oxymyoglobin (OMb) (quadratic, p = 0.10), as well as the total antioxidant capacity (T-AOC) activity (quadratic, p = 0.08) in the longissimus dorsi (LD) muscle. Further, dietary supplementation of 1% L-malic acid markedly increased the protein expression level of slow skeletal myosin heavy chain (MyHC) in the LD muscle (p < 0.05). Moreover, 0.5% and 2% L-malic acid supplementation significantly increased carcass length and loin eye area (p < 0.05). In conclusion, dietary L-malic acid could effectively improve the meat color and carcass traits of finishing pigs.

Novel slow-skeletal myosin ( MYH7) mutation in the original myosin storage myopathy kindred

Myosin storage myopathy (OMIM 608358), a congenital myopathy characterised by subsarcolemmal, hyaline-like accumulations of myosin in Type I muscle fibres, was first described by Cancilla and Colleagues in 1971 [Neurology 1971;21:579–585] in two siblings as ‘familial myopathy with probable lysis of myofibrils in type I muscle fibres’. Two mutations in the slow skeletal myosin heavy chain gene ( MYH7) have recently been associated with the disease in other families. We have identified a novel heterozygous Leu1793Pro mutation in MYH7 in DNA from paraffin sections of one of the original siblings. This historical molecular analysis confirms the original cases had myosin storage myopathy.

Expression of slow skeletal myosin heavy chain 2 gene in Purkinje fiber cells in chick heart

In avian, there are three slow skeletal myosin heavy chain (MHC) isoforms, slow skeletal MHC 1, 2, and 3. While slow skeletal MHC 3 has been characterized, slow skeletal MHC 1 and 2 are not yet fully studied. To determine the complete sequence of slow skeletal MHC 2, we isolated six overlapping cDNA clones, each encoding a portion of chick slow skeletal MHC 2, using the reverse transcription polymerase chain reaction (RT-PCR). The entire slow skeletal MHC 2 cDNA consisted of 5927 nucleotides including a 104 bp 3’-untranslated region and encoded 1941 amino acids. Using one of the cDNA clones, we made a probe for in situ hybridization. We also used immunohistochemistry to localize slow skeletal MHC 2 in skeletal and cardiac tissues. These studies showed that in addition to its expected expression in the adult chicken slow skeletal muscle, slow skeletal MHC 2 was expressed in the subendocardial cluster of cells and around the blood vessels within the ventricle of late embryos and adults. This isoform was not expressed in the myocardium throughout the life of the chicken. Based on morphological criteria as well as rich desmin expression, we concluded that the subendocardial cluster of cells were Purkinje cells. Although the physiological significance of the slow skeletal MHC expression remains elusive at this time, this MHC isoform may be used as a specific marker for Purkinje cells.

Localization of myotonic dystrophy protein kinase in skeletal muscle and its alteration with disease

Myotonic dystrophy (DM) is an autosomal dominant disorder which affects skeletal muscle, heart, eye lens, brain, and endocrine functions. The disease-causing mutations are expansions of the triplet repeat CTG in the 3' untranslated region of a locus which encodes a serine/threonine protein kinase that represents a new family of protein kinases. A monoclonal antibody to a recombinant DM protein kinase (mAb DM-1) reacts specifically with the 64 kDa isoform of DM protein kinase in type I fibers in skeletal muscle, the fiber type which characteristically atrophies in the disease. Within type I fibers of normal muscle the isoform may be localized with mAb DM-1 to the triad region. In the DM disease state, the enzyme is redistributed to the pathologically characteristic peripheral sarcoplasmic masses. In markedly affected human distal myotonic muscle, the levels of the 64 kDa DM kinase isoform are elevated relative to slow skeletal myosin heavy chain. These results suggest that, consistent with the dominant clinical phenotype, the localization and accumulation of the 64 kDa isoform are altered in the heterozygous disease state.

Changes in the distribution of slow skeletal myosin heavy chain SM1 in developing avian muscle fibres

The use of monoclonal antibodies against fast skeletal and slow skeletal myosin heavy chains (MHC) has shown the presence of significant amounts of slow skeletal type MHC in embryonic skeletal muscles of white leghorn chickens. The presence of this slow skeletal myosin heavy chain (SMHC) was not restricted to presumptive slow muscles only, as it was also observed in presumptive fast skeletal muscles. As was the case for embryonic MHC reactive with the antibody against fast skeletal myosin heavy chain (FMHC), the presence of SMHC could be detected at the earliest stages of myogenesis. It appeared to be present in most muscle cells during early embryonic development. The changes in its cellular distribution during subsequent embryonic and post-hatch period indicated its suppression in a certain proportion of the cells in both presumptive fast and slow skeletal muscles. Its time course of suppression, however, was much prolonged, not synchronized, and varied in fast and slow skeletal muscles during both embryonic and post-hatch development.

Selective synthesis and degradation of slow skeletal myosin heavy chains in developing muscle fibers.

During fetal development of fast skeletal muscles in the rat, three types of cells could be identified using a monoclonal antibody to slow skeletal muscle myosin heavy chain. Presumptive type I cells stained positive for slow forms of skeletal myosin heavy chain and a previously described protein of an apparent molecular weight of 100 KD, whereas presumptive type 2B cells did not stain for either of these peptides. Presumptive type 2A cells, on the other hand, did not stain for slow isoform of 100-K protein, but did stain positive for slow skeletal myosin heavy chain. There was a progressive suppression or degradation of slow skeletal myosin heavy chain in presumptive type 2A cells during subsequent fetal development, so that it was almost undetectable in most animals at birth. Soleus, a slow muscle, however, did not show clear differentiation into presumptive type I and type 2 cells until 4 days after birth.