Comparing the mRNA Expression Profile of Psoas Major and Longissimus Dorsi Muscles in Pig

To explore the differentially expressed mRNAs between oxidative and glycolytic muscles, Qianbei black pigs were slaughtered and longissimus dorsi muscle (LDM) and psoas major muscle (PMM) were selected and sequenced using Illumina Hiseq TM 4000. Bioinformatics analysis and differentially expressed genes were analyzed by GO and KEGG. qRT-PCR was used to validate the RNA-seq result. As a result, 69 differentially expressed genes were identified, with 46 down regulated genes and 23 up regulated genes in LDM versus PMM, which were categorized into 44 functional groups under three GO classifications. KEGG pathway analysis revealed 20 pathways were enriched. qRT-PCR shows the expression trends of ND6, MYH7, TBX1, FOS and SLC7A5 are consist with the RNA-seq result. We speculated these five genes may involve in differentiation of muscle cells, metabolism of carbohydrate and lipid, deposits of intramuscular fat and transformation of different types of muscle fibers.

Analysis of Titin in Red and White Muscles: Crucial Role on Muscle Contractions Using a Fish Model

Several studies have compared molecular components between red and white skeletal muscles in mammals. However, mammalian skeletal muscles are composed of mixed types of muscle fibers. In the current study, we analyzed and compared the distributions of titin, lipid, phosphate ions, and fatty acid levels in red and white muscles using a fish model (Tilapia), which is rich in red and white muscles, and these are well separated. Oil-red O staining showed that red muscle had more-abundant lipids than did white muscle. A time-of-flight secondary-ion mass spectrometric (TOF-SIMS) analysis revealed that red muscle possessed high levels of palmitic acid and oleic acid, but white muscle contained more phosphate ions. Moreover, elastica-van Gieson (EVG) and Mito-Tracker green FM staining showed that collagen and elastic fibers were highly, respectively, distributed in connective tissues and mitochondria in red muscle. An electron micrographic analysis indicated that red muscle had a relatively higher number of mitochondria and longer sarcomere lengths and Z-line widths, while myofibril diameters were thicker in white muscle. Myofibrillar proteins separated by SDS-PAGE showed that the major giant protein, titin, was highly expressed in white muscle than in red muscle. Furthermore, ratios of titin to myosin heavy chain (MHC) (titin/MHC) were about 1.3 times higher in white muscle than red muscle. We postulated that white muscle is fit for short and strong contractile performance due to high levels of titin and condensed sarcomeres, whereas red muscle is fit for low intensity and long-lasting activity due to high levels of lipids and mitochondria and long sarcomeres.

PO-089 Effects of 6-days nitrate supplementation on [Ca2+] and CRT in skeletal muscle of exhausted rats

Objective There are many active ingredients in sports nutrition, and nitrate is gradually being valued by sports nutrition and product developers. Supplementation of nitrate is a practical method to increase circulating plasma nitrite, thereby increasing NO bioavailability. However, the existing research has rarely reported the dose effect between nitrate supplementation and changes in exercise efficiency and capacity. The mechanism of action of nitrate is not fully understood yet. The aim of this study was to analyze the effects of different doses of nitrate on the exercise capacity of rats, as well as the detection of [Ca2+] and calreticulin (CRT) expression in the gastrocnemius, soleus and extensor digitorum longus, trying to figure out the effects of different doses of nitrate supplementation on calcium homeostasis in different types of muscle fibers. Methods 40 SD rats (8-week-old) weighing 270-290 grams were randomly divided into control group (C group, 8), exercise control group (EC group, 8), exercise with low-dose supplementation group (ELN group, 8), exercise with medium-dose supplementation group (EMN group, 8) and exercise with high-dose supplementation group (EHN group, 8). Sodium nitrate was used as exogenous nitrate for oral gavage. The intragastric concentration was 0.3 mmol/day/kg body weight in the ELN group, 0.7 mmol/day/kg body weight in the EMN group, and 1.0 mmol/day/kg body weight in the EHN group. The others were orally administered with normal saline. All exercise groups (EC, ELN, EMN and EHN) underwent 3 days adaptive low-intensity treadmill training with slope 0°, speed 16 meter/min, and the time is 5 min, 10 min and 15 min incrementally. 24 hours after the end of the last gavage, a one-time exhaustion treadmill experiment was started. The running platform slope was -16°, the speed was 16 meter/min. Exhaustive experiment participants were not aware of the grouping of rats. Immediately after the end of exhaustive exercise, the rats were weighed and anesthetized with sodium pentobarbital solution. Blood is collected for testing [NO2-]. The gastrocnemius, soleus and extensor digitorum longus were collected for testing NOS activity, tissue [Ca2+] and CRT expression. Results (1) Compared with the EC group, the exhaustion time of the other exercise groups was prolonged. The exhaustion time of the EMN group was very significantly prolonged from that of the EC group (P<0.01). The exhaustion time of the EMN group was significantly prolonged from that of the EC group (P< 0.05). At the same time, the difference between the EMN group and the ELN group was statistically significant (P<0.05). (2) Serum [NO2-] in the supplemented nitrate groups (ELN, EMN and EHN) was higher than that in the EC group, and the difference was statistically significant (P<0.01). The serum [NO2-] in different groups (ELN, EMN and EHN) raised with the increase of nitrate concentration, and the difference between each adjacent concentration group was statistically significant (P<0.05). (3) In the gastrocnemius, soleus and extensor digitorum longus respectively, there were no significant differences in TNOS, iNOS and cNOS activities between the groups (P>0.05). (4) In the gastrocnemius, compared with the EC group, the [Ca2+] (P<0.05) and CRT expression (P<0.05) in the EMN group were significantly decreased. There was no difference between the ELN vs EC group (P>0.05) and the EHN vs EC group (P>0.05). (5) In the soleus, the [Ca2+] (P<0.05) and CRT expression (P<0.05) in the EMN group were significantly decreased. There was no difference between the ELN vs EC group (P>0.05) and the EHN vs EC group (P>0.05). (6) In the extensor digitorum longus, compared with the EC group, the [Ca2+] (P<0.05) and CRT expression (P<0.05) in the EHN group were significantly decreased. There was no difference between ELN and EC group (P>0.05). The expression of CRT in EMN group was significantly decreased (P<0.05), but there is no difference of [Ca2+] between EMN and EC group (P<0.05). Conclusions (1) 6-day sodium nitrate supplementation is a reliable method to increase serum [NO2-] concentration. (2) 6-day sodium nitrate supplementation can prolong the duration of one-time exhaustive exercise in rats, and the dose of 0.7mmol/kg/d is the best. (3) Sodium nitrate supplementation can affect the [Ca2+] and the expression of CRT in skeletal muscle after one-time exhaustive exercise. Different concentrations of sodium nitrate have different effects on different types of muscle fibers.

Revisiting the peculiar regional distribution of muscle fiber types in rat Sternomastoid Muscle

The sternomastoid (SM) muscle in rodents is known to have a peculiar distribution of fiber types with a steep gradient from surface to deep region. We here further characterize this peculiar regional distribution by quantitative histochemical morphometrys. In Hematoxylin-Eosin (H-E) stained transverse cryosections harvested in the medial portion of the muscle we counted around 10.000 myofibers with a mean diameter of 51.3±12.6 (μm). Cryisections of the SM stained by SDH reaction clearly show two distinct regions, toward the deep surface of the muscle a 40% area that contains packed SDH-positive myofibers, while the remaining area of the SM toward the external surface presents a more checker-board appearance. On the other hand, in the deep region of SM type 1 (slow contracting) muscle fibers, caracterized by positive acidic ATPase pH 4.35 reaction, are only the 24.5% of the fibers in the deep area of SM muscles, being restricted to the deepest region. The 75.5% of the myofibers in the deep region are of the fast contracting types (either 48.4% 2A, SDH –positive fibers or 27.1% 2B, SDH-negative fibers, respectively). As expected the 2B muscle fibers, acidic ATPase pH 4.3-negative and SDH-negative, present the largest size, while Type 1 fibers, acidic ATPase pH 4.3-positive and SDH-positive, present the smallest size in rat SM muscle. Based on present and previous observations, comparison of change in absolute number and/or percentage of the fiber types in any experimental model of muscle atrophy/hypertrophy/plasticity/pathology /recovery in the rat SM, and possibly of all mammals, will ask for morphometry of the whole muscle cross-sections, muscle sampling by bioptic approches will provide only comparable data on the size of the different types of muscle fibers.

The Motor Unit and Orderly Recruitment

The physiological, metabolic, and anatomical properties of fast- and slow-twitch skeletal muscle fibers are detailed. How the proportions of different types of muscle fibers in a muscle are matched to the functions of that muscle is described. The important concept of the motor unit consisting of the motoneuron and all the muscle fibers it innervates is introduced. The roles of warm-up, orderly recruitment, and tetanus in determining muscle force are elaborated. Examples of muscle fiber recruitment and de-recruitment during natural movements before and after weight-lifting exercise are presented. The large effects of small changes in motoneuron discharge on resulting muscle tension are discussed in the context of exercise and disease. Differences between extraocular and other skeletal muscles in composition and innervation have clinical implications. Finally, students are introduced to electromyography, a minimally invasive clinical test that can be used to assess motor unit function and reveal fibrillations.

Standardization of metachromatic staining method of myofibrillar ATPase activity of myosin to skeletal striated muscle of mules and donkeys

This study aims at standardizing the pre-incubation and incubation pH and temperature used in the metachromatic staining method of myofibrillar ATPase activity of myosin (mATPase) used for asses and mules. Twenty four donkeys and 10 mules, seven females and three males, were used in the study. From each animal, fragments from the Gluteus medius muscle were collected and percutaneous muscle biopsy was performed using a 6.0-mm Bergström-type needle. In addition to the metachromatic staining method of mATPase, the technique of nicotinamide adenine dinucleotide tetrazolium reductase (NADH-TR) was also performed to confirm the histochemical data. The histochemical result of mATPase for acidic pre-incubation (pH=4.50) and alkaline incubation (pH=10.50), at a temperature of 37ºC, yielded the best differentiation of fibers stained with toluidine blue. Muscle fibers were identified according to the following colors: type I (oxidative, light blue), type IIA (oxidative-glycolytic, intermediate blue) and type IIX (glycolytic, dark blue). There are no reports in the literature regarding the characterization and distribution of different types of muscle fibers used by donkeys and mules when performing traction work, cargo transportation, endurance sports (horseback riding) and marching competitions. Therefore, this study is the first report on the standardization of the mATPase technique for donkeys and mules.

Assessment of the strength of the pelvic floor musculature in women who practice Mat Pilates.

Introduction: The Pilates Method is a program of physical and mental training that works the body as a whole, aiming to gain muscle strength, mainly at the central region formed by the abdominal muscles, spine and pelvic floor, and to promote stretching and flexibility. Objective: To investigate the effects of this technique in the pelvic floor muscle activity, noting the type of fiber was more work during the practice of this activities in soil (Mat Pilates). Method: It was a character study of interventional, observational, descriptive, conducted during the months from March to May 2011, in which six women aged between 35 and 65 years, who underwent Mat Pilates classes twice a week, was rated the strength of pelvic floor, by Perina®perineometer pressure before and after the eight classes. Results: It was observed that all the volunteers had gained in strength in both types of muscle fibers, and 84% (p < 0.05) had greater gain in type 2 fibers. Conclusion: The Mat Pilates to increase the influence of the pelvic floor muscle strength it and can be used to prevent dysfunctions dysfunction of these muscles.

Development of a Two-Dimensional Model of the Human Arm to Investigate the Biomimetic Substitution of Human Bicep Muscle With a Dielectric Electroactive Polymer Muscle Actuator

Current prostheses are not able to meet the needs of patients. The authors have recently been investigating the feasibility of integrating multiple types of electroactive polymers (EAP) to develop an artificial muscle for prostheses and muscle implants; much like biological muscle is made up of multiple types of muscle fibers. The intent is to produce a lightweight device which has smooth fluid-like motion, in contrast to the jerky motion of current prostheses which use heavy rotary actuators. A human arm model, isolating the bicep muscle, was developed to better understand the requirements on force and strain that an artificial muscle must meet to replace biological muscle. This study was conducted with the assistance of orthopedic surgeons from the Rochester General Hospital. Bicep muscle characteristics were compared with those of dielectric elastomer electroactive polymers (DEAP), since they produce relatively high force and large strain during actuation. Results show that current characteristics of DEAPs will not allow for direct substitution of human muscle fibers with EAPs because their force and strain outputs are too low. To increase the force and strain output of DEAPs to that of human muscle fibers, the stiffness of the DEAP needs to be increased. The analysis done and results obtained are discussed in the paper, as well as possible ways to increase the stiffness of EAPs to better meet the requirements for biological muscle replacement.

Композиція та гісто-ультраструктурна будова прямого м’яза стегна в нормі

The information on histometric and electron microscopic study of the muscle fibers of the rats’ rectus femoris in the norm is presented. The basic types of muscle fibers and their composition are described. The composition reflects the close morphological interdependence of the structure of myoneural junctions and elements of muscular tissue. It may determine different patterns of both reactive and destructive processes in the skeletal muscles.