Myosin Heavy Chain Type Research Articles

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.

Increasing myosin light chain 3f (MLC3f) protects against a decline in contractile velocity

Disuse induces adaptations in skeletal muscle, which lead to muscle deterioration. Hindlimb-unloading (HU) is a well-established model to investigate cellular mechanisms responsible for disuse-induced skeletal muscle dysfunction. In myosin heavy chain (MHC) type IIB fibers HU induces a reduction in contraction speed (Vo) and a reduction in the relative myosin light chain 3f (MLC3f) protein content compared with myosin light chain 1f (MLC1f) protein. This study tested the hypothesis that increasing the relative MLC3f protein content via rAd-MLC3f vector delivery would attenuate the HU-induced decline in Vo in single MHC type IIB fibers. Fischer-344 rats were randomly assigned to one of three groups: control, HU for 7 days, and HU for 7 days plus rAd-MLC3f. The semimembranosus muscles were injected with rAd-MLC3f (3.75 x 1011–5 x 1011 ifu/ml) at four days after the initiation of HU. In single MHC type IIB fibers the relative MLC3f content decreased by 25% (12.00±0.60% to 9.06±0.66%) and Vo was reduced by 29% (3.22±0.14fl/s vs. 2.27±0.08fl/s) with HU compared to the control group. The rAd-MLC3f injection resulted in an increase in the relative MLC3f content (12.26±1.19%) and a concomitant increase in Vo (2.90±0.15fl/s) of MHC type IIB fibers. A positive relationship was observed between the percent of MLC3f content and Vo. Maximal isometric force and specific tension were reduced with HU by 49% (741.45±44.24μN to 379.09±23.77μN) and 33% (97.58±4.25kN/m2 to 65.05±2.71kN/m2), respectively compared to the control group. The rAd-MLC3f injection did not change the HU-induced decline in force or specific tension. Collectively, these results indicate that rAd-MLC3f injection rescues hindlimb unloading-induced decline in Vo in MHC type IIB single muscle fibers.

Integrin-α7 signaling regulates connexin 43, M-cadherin, and myoblast fusion.

Regenerative medicine treatments for severe skeletal muscle injuries are limited, resulting in persistent functional deficits. Clinical options include neglecting the wound with the expectation that fibrosis will develop or using an autologous muscle graft with minimal functional improvement. A regenerative matrix can be used, but muscle fiber development on these matrices remains a challenge in vivo. Here, we explored the fundamental mechanisms that mediate cell-substrate signaling and its effect on cell-cell communication during myoblast fusion and tube formation to improve outcomes following implantation of matrices used to stimulate muscle regeneration. We previously reported that integrin-α7 was increased on anisotropic biomaterials, suggesting a role for α7β1 signaling in myoblast communication via connexin 43 and M-cadherin. Our results demonstrated that α7 silencing blocked expression of myogenic differentiation factor 1 (Myod), myogenin (Myog), myogenic factor 6 (Myf6), myosin heavy chain type 1 (Myh1), and transmembrane protein 8c (Tmem8c), indicating that myoblast fusion was inhibited. Expression of α5 and M-cadherin decreased but β1 and connexin 43 increased. We examined protein production and observed reduced extracellular-signal regulated kinase 1/2 (ERK) in α7-silenced cells that correlated with upregulation of connexin 43 and M-cadherin, suggesting a compensatory pathway. These results indicate that α7 signaling plays a critical role in ex vivo fusion and implicates a relationship with connexin 43 and M-cadherin.

Proteome modifications of Pacific white shrimp (Litopenaeus vannamei) muscle under biofloc system

The objective of the study was to examine the effects of biofloc technology on the muscle proteome of Litopenaeus vannamei. Two biofloc treatments and one control were compared: biofloc‐based tanks under zero‐water exchange fed with 150 g/kg crude protein (BF15), or with 250 g/kg crude protein (BF25) diets, and clear water tanks with 50% of daily water exchange stocked with shrimp fed with similar amount of a 250 g/kg crude protein diet, referred to as control. The shrimp (5.28 ± 0.42 g) were divided into the 300‐L fibreglass tanks (water volume of 200 L) at a density of 35 shrimp per tank and were cultured for 35 days. The biofloc groups displayed better growth and survival compared to the control. The muscle tissue from the control and BF25 groups was subjected to proteomic analysis. Lactate dehydrogenase, enolase, arginine kinase, mitochondrial ATP synthase subunit alpha, mitochondrial ATPase inhibitor factor 1 precursor, serpin 3 and myeloid differentiation factor 88 had an increased abundance in the BF25 group, while myosin heavy chain type 1 and myosin heavy chain type 2 showed a decreased abundance. The results indicate that biofloc technology could alter the expression of proteins involved in structure, metabolism and immune status of cultured shrimp.

Long-term insulin treatment leads to a change in myosin heavy chain fiber distribution in OLETF rat skeletal muscle.

The objective of this study was to investigate molecular and physiological changes in response to long-term insulin glargine treatment in the skeletal muscle of OLETF rats. Male Otsuka Long-Evans Tokushima Fatty (OLETF) and Long-Evans Tokushima Otsuka (LETO) rats aged 24 weeks were randomly allocated to either treatment with insulin for 24 weeks or no treatment, resulting in three groups. Insulin glargine treatment in OLETF rats (OLETF-G) for 24 weeks resulted in changes in blood glucose levels in intraperitoneal glucose tolerance tests compared with age-matched, untreated OLETF rats (OLETF-C), and the area under the curve was significantly decreased for OLETF-G rats compared with OLETF-C rats (P < 0.05). The protein levels of MHC isoforms were altered in gastrocnemius muscle of OLETF rats, and the proportions of myosin heavy chain type I and II fibers were lower and higher, respectively, in OLETF-G compared with OLETF-C rats. Activation of myokines (IL-6, IL-15, FNDC5, and myostatin) in gastrocnemius muscle was significantly inhibited in OLETF-G compared with OLETF-C rats ( P < 0.05). MyoD and myogenin levels were decreased, while IGF-I and GLUT4 levels were increased, in the skeletal muscle of OLETF-G rats ( P < 0.05). Insulin glargine treatment significantly increased the phosphorylation levels of AMPK, SIRT1, and PGC-1α. Together, our results suggested that changes in the distribution of fiber types by insulin glargine could result in downregulation of myokines and muscle regulatory proteins. The effects were likely associated with activation of the AMPK/SIRT1/PGC-1α signaling pathway. Changes in these proteins may at least partly explain the effect of insulin in skeletal muscle of diabetes mellitus.

Variation in mitochondrial respiratory capacity and myosin heavy chain composition in repeated muscle biopsies

Skeletal muscle is a heterogeneous tissue and it is essential to know the methodological variation and reliability when measuring aspects of muscle function. We assessed the methodological and biological variation when measuring mitochondrial respiratory capacity (MRC), citrate synthase (CS) activity and myosin heavy chain (MHC) composition in muscle biopsies from nine healthy male participants, and in addition we assessed variation in MRC in isolated mitochondria and yeast suspension. We analysed MRC, CS activity and MHC composition in duplicates (intra-biopsy variation) to quantify the methodological variation, as well as the biological variation from multiple muscle biopsies (inter-biopsy variation) obtained at different sites of the same muscle. Three muscle biopsies (B1, B2 and B3) were obtained from each subject in m. vastus lateralis. Two of the biopsies were from the same leg and one from the other leg.For MRC, intra-biopsy coefficient of variation (CV) was 8.4% and inter-biopsy CV was 13.3%. For MHC type I, IIa and IIx intra-biopsy CV was 8.3, 6.0 and 22.3%, respectively. Inter-biopsy CV for these MHC types were 21.5, 15.4 and 42.0%, respectively. For CS activity intra-biopsy CV was 0.6% and inter-biopsy CV was 15.3%. No differences between B1, B2 and B3 were detected for MRC, CS activity or MHC composition.

Long-Term Insulin Treatment Alters Muscle-Related Protein in OLETF Rat Skeletal Muscle

Purpose: The objective of this study was to investigate molecular and physiological changes in response to long-term insulin glargine treatment in the skeletal muscle of Otsuka Long-Evans Tokushima Fatty (OLETF) rats. Methods: Protein changes in the skeletal muscle of type 2 diabetic rats was detected by Western blot analysis, and muscle fiber type composition was assessed by real-time PCR. Results: Insulin glargine (1 U/kg) treatment in OLETF rats (OLETF-G) for 24 weeks were changed in blood glucose levels in intraperitoneal glucose tolerance tests compared with age-matched, untreated OLETF rats (OLETF-C), and the area under the curve was significantly decreased for OLETF-G rats compared with OLETF-C rats (P &amp;lt; 0.05). The protein levels of myosin heavy chain (MHC) isoforms were altered in gastrocnemius muscle of OLETF rats, and the proportions of MHC type I and II fibers were lower and higher, respectively, in OLETF-G compared with OLETF-C rats. Activation of myokines (interleukin [IL]-6, IL-15, fibronectin type III domain containing 5 [FNDC5]/irisin, and myostatin) in gastrocnemius muscle was significantly inhibited in OLETF-G compared with OLETF-C rats (P &amp;lt; 0.05). Moreover, myogenin determination gene D and myogenin levels were decreased, while insulin-like growth factor-I levels were increased, in the skeletal muscle of OLETF-G rats (P &amp;lt; 0.05). Insulin glargine treatment significantly increased the phosphorylation levels of 5’-AMP-activated protein kinase, sirtuin 1, and peroxisome proliferator-activated receptor γ coactivator 1α. Conclusions: Our results suggest that long-term insulin glargine treatment can effectively alter protein expression in the gastrocnemius muscle of OLETF rats. Disclosure H. Kwon: None. O. Hong: None. H. Kwon: None. Y. Kang: None. S. Lee: None. S. Kim: None. S. Yoo: None.

Aerobic Exercise Preconception and During Pregnancy Enhances Oxidative Capacity in the Hindlimb Muscles of Mice Offspring.

Liu, J, Lee, I, Feng, H-Z, Galen, SS, Hüttemann, PP, Perkins, GA, Jin, J-P, Hüttemann, M, and Malek, MH. Aerobic exercise preconception and during pregnancy enhances oxidative capacity in the hindlimb muscles of mice offspring. J Strength Cond Res 32(5): 1391-1403, 2018-Little is known about the effect of maternal exercise on offspring skeletal muscle health. The purpose of this study, therefore, was to determine whether maternal exercise (preconception and during pregnancy) alters offspring skeletal muscle capillarity and mitochondrial biogenesis. We hypothesized that offspring from exercised dams would have higher capillarity and mitochondrial density in the hindlimb muscles compared with offspring from sedentary dams. Female mice in the exercise condition had access to a running wheel in their individual cage 30 days before mating and throughout pregnancy, whereas the sedentary group did not have access to the running wheel before mating and during pregnancy. Male offspring from both groups were killed when they were 2 months old, and their tissues were analyzed. The results indicated no significant (p > 0.05) mean differences for capillarity density, capillarity-to-fiber ratio, or regulators of angiogenesis such as VEGF-A and TSP-1. Compared with offspring from sedentary dams, however, offspring from exercised dams had an increase in protein expression of myosin heavy chain type I (MHC I) (∼134%; p = 0.009), but no change in MHC II. For mitochondrial morphology, we found significant (all p-values ≤ 0.0124) increases in mitochondrial volume density (∼55%) and length (∼18%) as well as mitochondria per unit area (∼19%). For mitochondrial enzymes, there were also significant (all p-values ≤ 0.0058) increases in basal citrate synthase (∼79%) and cytochrome c oxidase activity (∼67%) in the nonoxidative muscle fibers as well as increases in basal (ATP) (∼52%). Last, there were also significant mean differences in protein expression for regulators (FIS1, Lon protease, and TFAM) of mitochondrial biogenesis. These findings suggest that maternal exercise before and during pregnancy enhances offspring skeletal muscle mitochondria functionality, but not capillarity.

Apigenin inhibits sciatic nerve denervation-induced muscle atrophy.

Apigenin (AP) has been reported to elicit anti-inflammatory effects. In this study, we investigated the effect of AP on sciatic nerve denervation-induced muscle atrophy. Sciatic nerve-denervated mice were fed a 0.1% AP-containing diet for 2 weeks. Muscle weight and cross-sectional area (CSA), and the expression of atrophic genes and inflammatory cytokines in the gastrocnemius were analyzed. Denervation significantly induced muscle atrophy. However, values for muscle weight and CSA were greater in the denervated muscle of the AP mice than the controls. AP suppressed the expression of MuRF1, but upregulated both myosin heavy chain (MHC) and MHC type IIb. AP also significantly suppressed expression of tumor necrosis-alpha in the gastrocnemius and soleus muscles, and interleukin-6 expression in the soleus muscle. AP appears to inhibit denervation-induced muscle atrophy, which may be due in part to its inhibitory effect on inflammatory processes within muscle. Muscle Nerve 58: 314-318, 2018.

Capillary density and succinate dehydrogenase in skeletal muscle on chronic kidney disease rats

Background and PurposeKidney disease increases risk of blood vessel and capillary disease. In case of chronic kidney disease (CKD), these problems may happen slowly over a long period of time. The thing about heart in particular is well known. Chronic kidney disease may be caused by diabetes, high blood pressure and other disorders. Hypertension causes CKD and CKD causes hypertension. Anyone can get CKD at any age and any sex. However, some people are more easily to get kidney disease than others. That two main causes of CKD are diabetes and high blood pressure. Those diseases fail with blood vessel and capillary in various factors. In any case, the blood vessel system is connected with kidney disease deeply. We confirmed muscle capillary architecture on rat last time. We clarified muscle capillary density and mitochondrial activity this time.Materials/Methods12 Wistar rats (age; 16wks) were randomly divided into CKD group (n=6) and Sham operation (SHAM) group (n=6). Rats in CKD group suffered from a chronic kidney failure artificially. The details are as follows; 1. When 16wks old, under anesthesia with pentobarbital, we removed the two‐third left kidney surgically. 2. When 17wks old, under anesthesia with pentobarbital, we removed the right kidney surgically. 3. When 23wks old, we removed soleus muscle out. 4. Those muscles were frozen, were stained by SDH, AP and ATPase (pH4.2) method, and observed with light microscope (LM). In SHAM group, they were operated for at the same time, but the kidney was not removed surgically. The kidney was extracted to outside from rat and it was returned to rat without removing it surgically. The microscope image of SDH stained was analyzed in NIH Image software and it was compared. All data were presented as the means ± SEM. All statistical tests were done using an unpaired Student's – test. P&lt;0.05 indicates a significant difference.ResultsOn 23 wks old CKD, body weight and soleus weight were decrease. Feeding volumes were same. Urinary albumin/urinary creatine value was increase. Data from measurement of the LM images by the NIH Image software of SDH, the mean SDH activity on CKD rats were significantly higher than that in the SHAM rats. Capillary density on CKD rat was lower than that in SHAM. However, muscle myosin heavy chain types of ratio on CKD were same to SHAM.ConclusionsThese results indicate that muscle requires oxygen, but shows that blood supply to muscle decreases on CKD.Support or Funding InformationThis study was supported by Grants‐in‐Aid for Scientific Research from the Japanese Ministry of Education, Culture, Sports, Science and Technology (Grant no. 17K01879)This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Aquaporin 4 expression in human skeletal muscle fiber types.

Aquaporins (AQPs) are a family of transmembrane proteins involved in the maintenance of osmotic gradients. AQP4 is abundant in skeletal muscle, where it seems to be associated with glycolytic metabolism. We investigated the pattern of expression of AQP4 in normal human myofibers relative to the main forms of myosin heavy chain (MHC). Six normal human muscle biopsies were analyzed by double immunofluorescence for co-expression of AQP4 and slow or fast MHC. A high percentage (64-99%) of MHC-fast positive fibers showed immunoreaction for AQP4. Immunoreactivity for AQP4 was also present in MHC-slow positive fibers, but with a higher variability (5-72%) among biopsies. The expression pattern of AQP4 in human myofibers is highly variable among different patients and cannot be predicted for single fibers depending on MHC type expression. Other factors, possibly related to muscle activity, may modulate AQP4 expression. Muscle Nerve 57: 856-859, 2018.

Phenotypic characterization of adenomyosis occurring at the inner and outer myometrium.

ObjectiveTo estimate the phenotypic characterization of fibrotic process in adenomyosis occurring at the inner or the outer myometrium.MethodsEight cases of adenomyosis occurring at the inner myometrium (Subtype I) and 10 cases of adenomyosis occurring at the outer myometrium (Subtype II), and 10 normal counterparts were used in this study. A immunohistochemical study for smooth muscle cells (SMCs) was performed using cytoskeletal proteins, Type I and III collagen, TGF-β and its signaling molecules.ResultsAn increased expression of Type I collagen was observed in the extracellular matrix of adenomyotic foci. In normal uteri, immunostaining of SMC differentiation marker proteins (Desmin, Smoothelin, Myosin heavy chain (MHC)) were absent or only found in low numbers at the inner myometrium, while all of these marker proteins were clearly stained at the outer myometrium. In both types of adenomyotic foci, Desmin, Smoothelin, and MHC commonly showed a negative staining at the adjacent area to the glands. A significant staining of Non-muscle myosin IIB, TGF-β, and phosphorylated TGF-β type I receptors were found only at the SMCs of Subtype II adenomyosis. The Smad3/2 ratio of Subtype II adenomyosis was significantly higher than that of Subtype I.ConclusionsThe inner myometrium of normal uteri was composed of undifferentiated phenotypes of SMCs, while the outer myometrium was composed of terminally differentiated SMCs. Various fibrotic processes have been suggested in the development of uterine adenomyosis. Distinct expression patterns of fibrosis related proteins have been shown to be implicated with differences in the subtypes of adenomyosis.

Differential impact of tongue exercise on intrinsic lingual muscles.

Aging is associated with muscle fiber hypotrophy and decreased percentages of rapidly contracting myosin heavy chain (MyHC) type IIb muscle fibers. Tongue exercise programs used to treat dysphagia target age-related decline in tongue muscle function, but the impact of exercise on the intrinsic tongue muscles is unknown. We hypothesized that exercise would induce muscle fiber hypertrophy and increase the percentage of MyHC IIa fibers in the intrinsic tongue. Animal model. Eight old and eight young-adult rats underwent 8 weeks of tongue exercise training, and 8 animals of each age group served as controls. Longitudinal, transverse, and verticalis muscle samples from the anterior, middle, and posterior regions of the tongue were sectioned and stained to determine muscle fiber diameter and MyHC composition. MyHC fiber type distribution was altered by exercise, and the effects differed by muscle and region of the tongue. In the exercise groups, as compared to the control groups, the anterior transverse and middle superior longitudinal muscles had significantly reduced percentages of MyHC IIx positive fibers and higher percentages of rapidly contracting fatigable MyHC IIb positive muscle fibers, whereas the middle transverse and posterior longitudinal muscles had increased percentages of the less rapidly contracting and more fatigue-resistant MyHC IIa fibers. The impact of exercise did not differ with age, as there was no significant interaction between age and exercise. Tongue exercise had no significant effect on muscle fiber diameter. The impact of exercise varied among the tongue muscles, which may indicate different functional contributions to the tongue exercise task. NA Laryngoscope, 128:2245-2251, 2018.

Noninvasive Assessment of Skeletal Muscle Myosin Heavy Chain Expression in Trained and Untrained Men.

Fry, AC, Housh, TJ, Cramer, JB, Weir, JP, Beck, TW, Schilling, BK, Miller, JD, and Nicoll, JX. Noninvasive assessment of skeletal muscle myosin heavy chain expression in trained and untrained men. J Strength Cond Res 31(9): 2355-2362, 2017-Numerous conditions and types of physical activity (e.g., exercise, aging, and muscle-related diseases) can influence muscle fiber types and the proteins expressed. To date, muscle fibers can only be characterized by actually obtaining a tissue sample using the invasive muscle biopsy procedure. Mechanomyography (MMG) is the assessment of the vibration properties of contracting skeletal muscle and has been proposed as a possible noninvasive method for muscle fiber analysis. Therefore, the purpose of this project was to examine the feasibility of using MMG and muscle performance measures to noninvasively assess muscle fiber characteristics. Fifteen men (5 endurance-trained, 5 weight-trained, and 5 sedentary) provided muscle samples from their vastus lateralis muscle. These samples were analyzed for relative myosin heavy chain (MHC) protein expression, which is highly correlated with % muscle fiber type areas. Additionally, each subject performed several muscle performance tests, and MMG of the quadriceps was assessed during a knee extension exercise. Multiple regression was used to develop prediction equations for determining relative muscle content of MHC types I, IIa, and IIx. A combination of MMG and knee extension performance variables estimated types I, IIa, and IIx MHCs with approximately 80% accuracy. Although preliminary, these data suggest that muscle performance tests in addition to MMG assessments during a simple muscle performance task (knee extension) can be used to estimate muscle fiber type composition in a healthy male population. Such methods could ultimately be used to noninvasively monitor muscle health and fitness.

Restoration of pharyngeal dilator muscle force in dystrophin-deficient (mdx) mice following co-treatment with neutralizing interleukin-6 receptor antibodies and urocortin 2.

What is the central question of this study? We previously reported impaired upper airway dilator muscle function in the mdx mouse model of Duchenne muscular dystrophy (DMD). Our aim was to assess the effect of blocking interleukin-6 receptor signalling and stimulating corticotrophin-releasing factor receptor 2 signalling on mdx sternohyoid muscle structure and function. What is the main finding and its importance? The interventional treatment had a positive inotropic effect on sternohyoid muscle force, restoring mechanical work and power to wild-type values, reduced myofibre central nucleation and preserved the myosin heavy chain type IIb fibre complement of mdx sternohyoid muscle. These data might have implications for development of pharmacotherapies for DMD with relevance to respiratory muscle performance. The mdx mouse model of Duchenne muscular dystrophy shows evidence of impaired pharyngeal dilator muscle function. We hypothesized that inflammatory and stress-related factors are implicated in airway dilator muscle dysfunction. Six-week-old mdx (n=26) and wild-type (WT; n=26) mice received either saline (0.9%w/v) or a co-administration of neutralizing interleukin-6 receptor antibodies (0.2mgkg-1 ) and corticotrophin-releasing factor receptor 2 agonist (urocortin 2; 30μgkg-1 ) over 2weeks. Sternohyoid muscle isometric and isotonic contractile function was examined ex vivo. Muscle fibre centronucleation and muscle cellular infiltration, collagen content, fibre-type distribution and fibre cross-sectional area were determined by histology and immunofluorescence. Muscle chemokine content was examined by use of a multiplex assay. Sternohyoid peak specific force at 100Hz was significantly reduced in mdx compared with WT. Drug treatment completely restored force in mdx sternohyoid to WT levels. The percentage of centrally nucleated muscle fibres was significantly increased in mdx, and this was partly ameliorated after drug treatment. The areal density of infiltrates and collagen content were significantly increased in mdx sternohyoid; both indices were unaffected by drug treatment. The abundance of myosin heavy chain type IIb fibres was significantly decreased in mdx sternohyoid; drug treatment preserved myosin heavy chain type IIb complement in mdx muscle. The chemokines macrophage inflammatory protein2, interferon-γ-induced protein10 and macrophage inflammatory protein3α were significantly increased in mdx sternohyoid compared with WT. Drug treatment significantly increased chemokine expression in mdx but not WT sternohyoid. Recovery of contractile function was impressive in our study, with implications for Duchenne muscular dystrophy. The precise molecular mechanisms by which the drug treatment exerts an inotropic effect on mdx sternohyoid muscle remain to be elucidated.

Effects of botulinum toxin type A injection for pathological characteristic of calf in rats with spinal cord injure

Objective: To explore the effect of BoTN-A on pathological characteristics of calf (GM) and motor function of ankle dorsiflexors in SCI model rats. Methods: Thirty-six SD male rats (weight 260-280 g) were randomly allocated into normal control group and 12w-control group, NS-injection group and BT-injection group in this study.NS/BT-injection groups were divided into two subgroups separately (2w-NS, 2w-BT, 8w-NS, 8w-BT). No injection was applied in normal control group or 12w-control group.Saline/BoTN-A was injected in right GM in NS/BT-injection group at two different time points(2w, 8w). GM and Sol on right side of rats would be forwarded for pathologicalexaminations, such as muscle weight, myosin heavy chain (MyHC) electrophoretic analysisat the 12th week. Results: Compared with the other three groups, the muscle weights of GM and Sol in the BT-injection group significantly decreased.MyHC type ratioof GM and Sol on the right side in the BT-injection group also significantlychanged.According to subgroup comparisons, MyHC type ratio of GM and Sol on the injectedside in the 2w-BT subgroup was significant different from that of the 8w-BT subgroup.MyHC type ratios of GM on the non-injected side in the BT injection group also changed more than normal control group.The change of MyHC type ratio of non-injected GM was significantly higher in the 2 week-BT subgroup than that in the 8-week subgroup. Conclusions: BoNT-A intervention resulted in pathological changes not only in the injected GM in SCI rats, but also in non-injected GM and non-injected Sol.The effects of earlier (2 weeks) BoTN-A intervention on pathologic characteristicsof GM and Sol were larger than that of later intervention.

Fiber type composition of the palmaris brevis muscle: implications for palmar function.

The palmaris brevis (PB) is a small muscle of variant morphology located on the ulnar aspect of the palm, superficial to the hypothenar eminence. Functionally, the PB has been proposed to protect the neurovasculature of the ulnar canal from compressive forces during repetitive or intermittent trauma associated with grasping. Although PB function has been inferred from cadaveric observations, it is unknown whether it has the contractile capacity and fatigue-resistance necessary to withstand these functional demands. Insight into the functional specialization of the PB can be provided through investigating the proportions of type I and type II muscle fibers by staining for myosin heavy chain (MHC) isoforms using immunohistochemical methods. Therefore, the purpose of this study was to quantify the proportion of type I and type II muscle fibers to provide insight into the role of the PB in palmar function based on its gross histological structure. Sixteen PB specimens were harvested from the hands (eight right, eight left) of eight formalin-embalmed cadavers (mean age: 75±14years; three males, five females). PB muscle composition was determined by labeling serial cross-sections with MHC type I and type II monoclonal antibodies. The results indicate that the PB is primarily composed of type I muscle fibers (72.2±13.7%), with no significant differences between left and right hands. Given the predominance of type I muscle fibers, our findings indicate the PB may be fatigue-resistant and thus, capable of contracting for prolonged durations. This supports cadaveric observations indicating that the PB functions to protect the ulnar neurovasculature of the palm by providing a muscular barrier in addition to serving as a functional anchor to the hypothenar fat pad when objects are firmly compressed into the palm.

The effect of caloric restriction on the forelimb skeletal muscle fibers of the hypertrophic myostatin null mice

Skeletal muscle mass loss has a broad impact on body performance and physical activity. Muscle wasting occurs due to genetic mutation as in muscular dystrophy, age-related muscle loss (sarcopenia) as well as in chronic wasting disorders as in cancer cachexia. Food restriction reduces muscle mass underpinned by increased muscle protein break down. However the influence of dietary restriction on the morphometry and phenotype of forelimb muscles in a genetically modified myostatin null mice are not fully characterized. The effect of a five week dietary limitation on five anatomically and structurally different forelimb muscles was examined. C57/BL6 wild type (Mstn+/+) and myostatin null (Mstn−/−) mice were either given a standard rodent normal daily diet ad libitum (ND) or 60% food restriction (FR) for a 5 week period. M. triceps brachii Caput laterale (T.lateral), M. triceps brachii Caput longum (T.long), M. triceps brachii Caput mediale (T.medial), M. extensor carpi ulnaris (ECU) and M. flexor carpi ulnaris (FCU) were dissected, weighted and processed for immunohistochemistry. Muscle mass, fibers cross sectional areas (CSA) and myosin heavy chain types IIB, IIX, IIA and type I were analyzed. We provide evidence that caloric restriction results in muscle specific weight reduction with the fast myofibers being more prone to atrophy. We show that slow fibers are less liable to dietary restriction induced muscle atrophy. The effect of dietary restriction was more pronounced in Mstn−/− muscles to implicate the oxidative fibers compared to Mstn+/+. Furthermore, peripherally located myofibers are more susceptible to dietary induced reduction compared to deep fibers. We additionally report that dietary restriction alters the glycolytic phenotype of the Mstn−/− into the oxidative form in a muscle dependent manner. In summary our study shows that calorie restriction alters muscle fiber profile of forelimb muscles of Myostatin null mice.

Segmental Distribution of Myosin Heavy Chain Isoforms Within Single Muscle Fibers.

Despite many studies looking at the distribution of myosin heavy chain (MHC) isoforms across a transverse section of muscle, knowledge of MHC distribution along the longitudinal axis of a single skeletal muscle fiber has been relatively overlooked. Immunocytochemistry was performed on serial sections of rat extensor digitorum longus (EDL) muscle to identify MHC types I, IIA, IIX, IIY, and IIB. Sixteen fascicles which contained a total of 362 fibers were randomly and systematically sampled from the three EDL muscles. All MHC type I and type II isoforms were expressed. Segmental expression occurred within a very limited segment. MHC isoform expression followed the accepted traditional order from I⇔IIA⇔IIX⇔IIB, however, in some samples expression of an isoform was circumvented from IIB to I or from I to IIB directly. Segmental distribution of MHC isoforms along a single muscle fiber may be because of the myonuclear domain. Anat Rec, 300:1636-1642, 2017. © 2017 Wiley Periodicals, Inc.

The effect of different intensity exercise on skeletal muscle fiber MHC subtype transformation and CaN/NFATc1 signaling pathways

To study the effect of different intensity exercise on skeletal muscle fiber myosin heavy chain(MHC) subtype transformation and CaN/NFATc1 signaling pathways. Twenty-four Male SD rats (2-month old) were randomly divided into normal control group (NC), moderate intensity exercise group (ME, grade 5°, speed 18 m/min), heavy intensity exercise group (HE, grade 10°, 26.8 m/min). The rats in exercise groups were treated with treadmill training for eight weeks. The type I and type Ⅱ muscle fibers were determined by ATPase staining method. MHC subtype was separated by SDS-PAGE. The activity of CaN was determined by colorimetric method. The content of NFATc1 protein in skeletal muscle was detected by immune imprinting technology. ①Skeletal muscle fiber density changes:the type I and Ⅱ fiber number density of quadriceps in ME group were increased significantly (P<0.05), but in HE group, only the type Ⅱ fiber surface density was increased significantly (P<0.05). The type I fiber number density of soleus in ME and HE group was increased significantly (P<0.05). ②The changes of fibers MHC subtype percentage in skeletal muscle:the percentages of MHC I and type Ⅱa of quadriceps in ME group were increased (P<0.05), while the percentage of MHC Ⅱb was decrease (P<0.05). The percentage of MHC I in soleus was increased, while the percentages of MHCⅡa and Ⅱb were decreased. ③The activity of CaN and the content of NFATc1 protein in ME group were increased significantly (P<0.05). The heavy and moderate intensity exercise may induce skeletal muscle MHC type transforming from fast to slow. At the same time, the activity of CaN and the expression of NFATc1 protein are increased accompanying the changes of skeletal muscle fibers subtype.