OBJECTIVETo explore the relationship between contractile characteristics and fiber type conversion in hind-limb unloading mice soleus.

METHODSAfter 28-day hind-limb unloading and muscle atrophy, we used the method of isolated muscle perfusion with different stimulated protocols to determine the changes in contractile characteristics including the isometric twitch force and tetanus force and fatigue index of slow twitch muscle in mice. The muscle myofibrillar composition and fiber type conversion were detected by immunofluorescence staining and real-time PCR.

RESULTSThe isometric twitch force and the tetanus force and fatigue index were decreased progressively in 28-day unloaded mice soleus, with the increase in fast twitch fiber subtype and the decrease in slow twitch fiber subtype.

CONCLUSIONThe alteration of contractile characteristics is relevant to the slow-to-fast fiber conversion in mice soleus after 28-day hind-limb unloading.

Animals ; Hindlimb Suspension ; physiology ; Mice ; Mice, Inbred C57BL ; Muscle Contraction ; physiology ; Muscle Fatigue ; physiology ; Muscle Fibers, Fast-Twitch ; physiology ; Muscle Fibers, Slow-Twitch ; physiology ; Muscle, Skeletal ; pathology ; physiology ; Muscular Atrophy

Akt, a key protein of cell survival, can promote cell growth and survival by activations of various cellular protective factors. Ischemic preconditioning (IP) has been known to reduce ischemic injury through upregulation of phosphorylation of Akt (p-Akt). CuZn-superoxide dismutase (SOD-1), an antioxidant enzyme, scavenges reactive oxygen species and protects cell from oxidative stress by increasing the activaiton of Akt. The present study was performed to examine the effects of IP on the expression of p-Akt and SOD-1 in the ischemicreperfused rat skeletal muscles. Thirty weeks old male SD rats were divided into 4 groups, such as controls, IP, 4 hour ischemia and 4 hour ischemia with IP. For IP, commom iliac artery was occluded three times for 5 min ischemia followed by 5 min reperfusion using rodent vascular clamps. Ischemia was induced by occlusion on the same artery for 4 hours. The Tibialis anterior and Soleus were removed at 0, 1, 3, and 24 hours of reperfusion. The expressions of p-Akt (Ser 473) and SOD-1 were examined with immunohistochemistry and Western blot analysis.In the IP group, the p-Akt and SOD-1 were increased, compared to the control group. In the ischemia group, the p- Akt and SOD-1 were decreased, compared to the control group, and were more abundant when reperfusion time were increased. IP increased the p-Akt and SOD-1 after 4 hour ischemia, and the p-Akt and SOD-1 were higher in Soleus compared to Tibialis anterior. These findings suggest that IP increases p-Akt and expression of SOD-1 in the ischemic-reperfused rat skeletal muscles, and that upregulations of p-Akt and SOD-1 induced by IP were higher in the red muscle fiber, Soleus, than the white muscle fiber, Tibialis anterior.
Animals ; Arteries ; Blotting, Western ; Cell Survival ; Humans ; Iliac Artery ; Immunohistochemistry ; Ischemia ; Ischemic Preconditioning ; Male ; Muscle Fibers, Fast-Twitch ; Muscle Fibers, Slow-Twitch ; Muscle, Skeletal ; Oxidative Stress ; Phosphorylation ; Rats ; Reactive Oxygen Species ; Reperfusion ; Rodentia ; Up-Regulation

The elevated plasma level of thyroxin and/or triiodothyronine in hyperthyroidism not only induces a transition from the innervated slow-twitch muscle fibers to fast-twitch fibers, but also changes the contractile function in transition muscle fibers. So the muscle weakness of thyrotoxic myopathy would relate to alteration in fatigability of tetanic contraction in muscles, especially in slow-twitch fibers. The aim of the present study was to observe the extent of fatigue of soleus in 4-week hyperthyroid rats and elucidate its underlying mechanism. The isolated soleus muscle strips were perfused in Krebs-Henseleit solution with or without an inhibitor of sarcoplasmic reticulum Ca(2+)-ATPase (SERCA), cyclopiazonic acid (CPA). The contractile function of soleus was observed in twitch and intermittent tetanic contraction. The body weight in 4-week hyperthyroid rats decreased as compared with that in the control group [(292±13) g vs (354±10) g], but there was no difference between hyperthyroid and control groups in the wet weight of soleus [(107.3±8.6) mg vs (115.1±6.9) mg]. The time to peak tension (TPT) and time from peak tension to 75% relaxation (TR(75)) in twitch contraction were shortened in the soleus of hyperthyroid rats, and the TR(75) of tetanic contraction was also shortened as compared with that in the control group [(102.8±4.1) ms vs (178.8±15.8) ms]. The optimal stimulation frequency at which a maximal tension of tetanic contraction happened was shifted from 100 Hz in the control group to 140 Hz in hyperthyroid group. The soleus of hyperthyroid rat was easier to fatigue than that of the control rat during intermittent tetanic contraction. The SERCA activity also increased in soleus of hyperthyroid rat. The TR(75) in tetanic contraction was prolonged and showed an increased fatigue resistance in the soleus of control and hyperthyroid groups treated with 1.0 μmol/L CPA. The fatigue resistance of tetanic contraction in the soleus of hyperthyroid rat increased further with 5.0 μmol/L CPA treatment, but the resting tension kept rising. The 10 μmol/L CPA reduced the fatigue resistance of tetanic contraction in the soleus of hyperthyroid rat. The above results demonstrate that the SERCA activity in soleus can also influence the relaxation duration of twitch contraction like that in the myocardium. The SERCA activity in slow-twitch fibers is possibly involved in the regulation of fatigue resistance of intermittent tetanic contraction.
Animals ; Fatigue ; Glucose ; Hyperthyroidism ; enzymology ; In Vitro Techniques ; Muscle Contraction ; Muscle Fibers, Slow-Twitch ; enzymology ; physiology ; Muscle, Skeletal ; enzymology ; physiology ; Rats ; Sarcoplasmic Reticulum Calcium-Transporting ATPases ; metabolism ; Tromethamine

Congenital neuromuscular disease with uniform type 1 fiber (CNMDU1) is a rare but distinct form of nonprogressive, congenital myopathy. CMNDU1 is characterized by a type 1 muscle fiber content of more than 99%. This condition has only been previously described in a few reports. The authors report an 11-year-old girl who exhibited delayed developmental milestones, proximal muscle weakness, and bilateral ptosis. Her serum creatine kinase level was normal but an electromyographic study showed myopathic changes. A biopsy specimen from the left deltoid muscle revealed a uniformity of type 1 fibers (greater than 99%) with a moderate variation in fiber size. This is the first case of CNMDU1 reported in Korea.
Biopsy ; Child ; Developmental Disabilities/*pathology ; Female ; Human ; Muscle Fibers, Slow-Twitch/*pathology ; Muscle, Skeletal/*pathology ; Neuromuscular Diseases/congenital/*pathology

To investigate the morphological changes in skeletal muscle produced by colchicines toxicity, 42/rats were given a single intraperitoneal dose(0.4mg/Kg) of colchicines, and the animals were killed at daily intervals up to 7 days. The results of light microscopic and electron microscopic observations are summarized as follows; 1) At the light microscopic level, colchicines treated arts show non-inflammatory, nonspecific scattered degeneration or necrosis of myofibers irrespective of location of the skeletal muscle. No significant pathologic changes in peripheral nerve fibers distributed in affected muscles are seen. 2) The general ultrastructural changes are dilation of sarcoplasmic reticulum, swelling and pleomorphism of mitochondria, and appearance of membraneous bodies characterized by a single or multiple concentric layers of membranes in subsarcolemmal zones and intermyofibrillar zones, and focal necrosis or loss of myofibrils. The incidence and severity of these changes show gradual increase and reach maximal peak 3 days after colchicines administration, and then they show gradual decrease. Nerve fibers and motor-end plates show no difference compared with the control. 3) The observations are consistent with the opinion that the muscle weakness or paresis produced by toxic dose of colchicines is not of neuropathic, but of myopathic alterations. 4) The membraneous bodies are classified into the following 3 types;Type I is those bodies outlined by a few concentric membranes with osmiophilic granules, small vesicles, free ribosomes, and mitochondria in central zone. Type II is those outlined by several concentric layers of membranes with osmiophilic granules, small vesicles, free ribosomes, and mitochondria in center. Type III is those outlined by multilayered or thick concentric membranes with osmiophilic granules, small vesicles, free ribosomes, and mitochondria in central zone, frequently with complicated lamellar structures. 5) The skeletal muscle lesions produced by colchicines toxicity may be categorized into those degenerative changes characterized by the appearance of membraneous bodies. And, morphologically, it is presumed that the membraneous bodies are heterogenous in origin, alterations of subcellular structures such as sarcoplasmic reticulum, mitochondria, and lysosome.
Animals ; Colchicine* ; Incidence ; Lysosomes ; Membranes ; Mitochondria ; Muscle Weakness ; Muscle, Skeletal* ; Muscles ; Myofibrils ; Necrosis ; Nerve Fibers ; Paresis ; Peripheral Nerves ; Ribosomes ; Sarcoplasmic Reticulum

OBJECTIVETo observe the change of the muscular fiber phynotype at different condition of nerve injury.

METHODSRabbits were used as an animal model in this study. The trigeminus and facial nerves of the animal were simultaneously severed (group 1) or only the latter was severed (group 2). The morphologic change of the muscular fibers was observed with histochemical methods; the tension of contraction and the threshold value of electrical stimulation were observed with electrical physiological methods.

RESULTSTrigeminus nerve play an important role in delaying muscular atrophy after facial nerve was severed. The atrophy degree of type II a and II b muscular fibers was less in group 2 than that in group 1. The change of type 1 muscular fibers was not affected by trigeminus nerve. New muscular fibers emerged in group 2. The tension of contraction and the threshold value of electrical stimulation were better in group 2 than that of in group 1.

CONCLUSIONSSensory nerve could delay muscle atrophy after denervation. Sensory nerve should be repaired simultaneously when the motor nerve was sutured. The results of this study would facilitate clinical treatment for facial palsy.

Animals ; Denervation ; Disease Models, Animal ; Facial Nerve ; Facial Nerve Diseases ; pathology ; Female ; Muscle Fibers, Skeletal ; pathology ; Muscle Fibers, Slow-Twitch ; pathology ; Rabbits

Titin, the largest known protein in the body expressed in three isoforms (N2A, N2BA and N2B), is essential for muscle structure, force generation, conduction and regulation. Since the 1950s, muscle contraction mechanisms have been explained by the sliding filament theory involving thin and thick muscle filaments, while the contribution of cytoskeleton in force generation and conduction was ignored. With the discovery of insoluble protein residues and large molecular weight proteins in muscle fibers, the third myofilament, titin, has been identified and attracted a lot of interests. The development of single molecule mechanics and gene sequencing technology further contributed to the extensive studies on the arrangement, structure, elastic properties and components of titin in sarcomere. Therefore, this paper reviews the structure, isforms classification, elastic function and regulatory factors of titin, to provide better understanding of titin.
Connectin/genetics* ; Muscle Proteins/metabolism* ; Protein Isoforms/genetics* ; Sarcomeres/metabolism* ; Muscle Fibers, Skeletal/metabolism*

PURPOSE: The present study was designed to evaluate the effect of intermittent electrical stimulation (ES) of the sciatic nerve on the expression of neuronal nitric oxide synthase (nNOS) protein in the soleus and in the medial gastrocnemius muscles 2 weeks following hindlimb suspension (HS). MATERIALS AND METHODS: In the HS+ES group, a pair of stainless steel electrodes were placed at the midportion of the unilateral sciatic nerve during hindlimb unloading. Square wave pluses with a 5 seconds ON-OFF pattern were applied to the sciatic nerve 4 hours a day for 14 days. The electrical stimulation parameters were 20 Hz, 0.3 ms, 1-5 voltage. 14 days later the sciatic nerve stimulation maximal twitch response was measured in the soleus and medial gastrocnemius muscles using an isometric tension transducer and polygraph. Western blot was used to analyze the expression of nitric oxide synthase (nNOS) protein in hindlimb muscles. RESULTS: The soleus muscle consisted of slow-twitch muscle fiber and showed a prominent decrease in maximum twitch tension and muscle weight than the medial gastrocnemius muscle 2 weeks after hindlimbs suspension. Hindlimbs suspension caused a reduction in the relative quantity of nNOS protein by 89% and 55% in the soleus and the medial gastrocnemius muscles, respectively, after 2 weeks of unloading compared with the ambulatory controls. However, intermittent electrical stimulation of the sciatic nerve delayed reduction significantly with respect to the expression of nNOS protein and twitch tension during hindlimb unloading. CONCLUSION: The results suggest that application of electrical stimulation to the sciatic nerve has a significant effect on NO signal transduction by regulating nNOS expression in atrophied hindlimb extensor muscles.
Animals ; Blotting, Western ; Electric Stimulation* ; Electrodes ; Hindlimb Suspension* ; Hindlimb* ; Muscle Fibers, Slow-Twitch ; Muscle, Skeletal ; Muscles* ; Muscular Atrophy ; Neurons* ; Nitric Oxide Synthase ; Nitric Oxide Synthase Type I* ; Rats* ; Sciatic Nerve* ; Signal Transduction ; Stainless Steel ; Transducers

In an attempt to clarify the function of the suboccipital muscles, we performed morphological observation of the suboccipital muscles for variations in the muscle belly and compared the morphology of their muscle fibers in terms of cross-sectional area by immunostaining with anti-myosin heavy chain antibodies. The cadavers of 25 Japanese individuals were used: 22 for morphological examinations and three for histological examinations. Among samples of the rectus capitis posterior major muscle (RCPma) and rectus capitis posterior minor muscle (RCPmi), 86.4% had a typical muscle appearance with a single belly, and 13.6% had an anomalous morphology. None of the samples of the obliquus capitis superior (OCS) or obliquus capitis inferior (OCI) muscles had an anomalous appearance. Measurement of cross-sectional area revealed that fast-twitch muscle fibers in the RCPma and OCI had a significantly greater cross-sectional area than those of the RCPmi and OCS. The cross-sectional area of intermediate muscle fibers was also significantly greater in the OCS than in the RCPma, RCPmi, and OCI. The cross-sectional area of slow-twitch muscle fibers was significantly greater in the OCS than in the RCPma, RCPmi, and OCI, and the RCPmi showed a significantly greater cross-sectional area for slow-twitch muscle fibers than did the RCPma, and OCI. Our findings indicate that the RCPmi and OCS exert a greater force than the RCPma and OCI, and act as anti-gravity agonist muscles of the head. Prolonged head extension in individuals with anomalous suboccipital muscle groups could result in dysfunction due to undue stress.
Antibodies ; Asian Continental Ancestry Group ; Cadaver ; Classification* ; Head ; Headache ; Humans ; Muscle Fibers, Fast-Twitch ; Muscle Fibers, Slow-Twitch ; Muscles

Aging has become an important topic for scientific research because life expectancy and the number of men and women in older age groups have increased dramatically in the last century. This is true in most countries of the world including the Republic of Korea and the United States. From a rehabilitation perspective, the most important associated issue is a progressive decline in functional capacity and independence. Sarcopenia is partly responsible for this decline. Many changes underlying the loss of muscle mass and force-generating capacity of skeletal muscle can be understood at the cellular and molecular levels. Muscle size and architecture are both altered with advanced adult age. Further, changes in myofibers include impairments in several physiological domains including muscle fiber activation, excitation-contraction coupling, actin-myosin cross-bridge interaction, energy production, and repair and regeneration. A thorough understanding of these alterations can lead to the design of improved preventative and rehabilitative interventions, such as personalized exercise training programs.
Adult ; Aged ; Aging* ; Education ; Female ; Humans ; Life Expectancy ; Male ; Muscle Fibers, Skeletal* ; Muscle, Skeletal ; Myofibrils ; Regeneration ; Rehabilitation ; Republic of Korea ; Sarcopenia ; United States