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

The tunica muscularis of the esophagus of rodents is entirely striated and changes to smooth muscle near the esophago-gastric junction (EGJ). The changing pattern of two types of muscles, however, have not been defined. And the existence of an anatomical sphincter at the EGJ is still a matter of uncertainty. The present study was undertaken to describe the changing pattern of skeleto-smooth muscles and to verify whether anatomical sphincter exists at EGJ in the rat and mongolian gerbil. By light microscopy, with H-E and PTAH stains, the muscle fibers consisting muscularis externa of the esophagus were entirely striated both in rat and mongolian gerbil, and abruptly changes to smooth muscle in the EGJ. A demarcation line between two types is relatively clear, but small fibers were intermingled with each other. The increase in thickness of the circular muscle layer near the EGJ was not found. Immunocytochemistry revealed that desmin was strongly positive in striated muscle fiber and positive different intensities from fiber to fiber in smooth muscle. Vimentin immuno-reactivity, however, was negative both in striated and smooth muscle. There was no racial differences in desmin and vimentin immunohisto-chemistries. By electron microscopy, there were several patterns in skeleto-smooth muscle transition: most of skeletal muscle was clearly demarcated with smooth muscle by interstitial cell and connective tissue; the skeletal and smooth muscle fibers were arranged parallel. The skeletal muscle fiber was separated from the smooth muscle fiber by long slender process of intersitial cell; the skeletal muscle fiber was interposed into wedge shaped branching smooth muscle fiber, or reverse. The typical neuro-muscular junction was found in the skeletal muscle. Smooth muscle fiber contacted with nerve varicosities and the process of interstitial cell. The smooth muscle fibers below the EGJ contracted and appeared irregular in outline. These results show the changing pattern of skeleto-smooth muscle fibers in muscularis externa of the esophagus of rodents, and suggest that the anatomical sphincter may be present at the EGJ.
Animals ; Coloring Agents ; Connective Tissue ; Desmin ; Esophagus ; Gerbillinae ; Immunohistochemistry ; Microscopy ; Microscopy, Electron ; Muscle Fibers, Skeletal ; Muscle, Skeletal ; Muscle, Smooth ; Muscle, Striated ; Muscles ; Rats ; Rodentia* ; Uncertainty ; Vimentin

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

Neuromuscular choristoma is a rare benign tumor of the peripheral nerves. To the best of our knowledge, 21 cases have been reported to date. We describe here a 20-day-old female infant who presented with a buttock mass (4.5 x 4.1 x 3.2 cm on MRI) arising from the left sciatic nerve. Microscopically, it was characterized by an intimately disorganized mixture of nerve fibers and striated muscle fibers that were occasionally surrounded by the perineurium and separated by fibrous bands of varying thickness. In some areas, there appeared to be some cells in transitional forms between nerve fibers and muscle fibers, revealing variously positive expressions for S-100 protein in the muscular components. These findings are consistent with the hypothesis that neuroectodermal-derived Schwann cells can give rise to mature skeletal muscle. It appears that the fibrosis may be related to the degeneration of the neural components. The size of the mass on MRI has been unchanged during the 3-year follow-up period.
Buttocks ; Choristoma* ; Female ; Fibrosis ; Follow-Up Studies ; Humans ; Infant ; Magnetic Resonance Imaging ; Muscle, Skeletal ; Muscle, Striated ; Nerve Fibers ; Peripheral Nerves ; S100 Proteins ; Schwann Cells ; Sciatic Nerve*

PURPOSE: The intermediate filament proteins, desmin and vimentin, are specific components of the cytoskeleton of striated muscle fibers and of mononuclear cells of mesenchymal origin including myoblasts, respectively. Desmin has also been found in presumptive myoblasts of mammals. The aim of this experiment was attempted to observe the phenotypic changes of intermediate filaments in skeletal muscle fibers during early stages of sciatic nerve crushing injury. MATERIALS AND METHODS: The sciatic nerves of rats were surgically crushed by hemostat and serial cryosections of soleus and extensor digitorum longus(EDL) muscles were prepared at 2, 4, 6, 8, 10, 15, 20 and 27 days after nerve injury. Serial cryosections were immunolabelled with desmin, vimentin and laminin and were histochemically reacted with NADH-TR. RESULTS: 1) Firstly, desmin positive fibers were appeared in fast-twitch type C fibers of both muscles at 6 days after nerve crushing, but were not reacted for vimentin. 2) Co-expressions of desmin and vimentin were firstly detected in fast-twitch type A fibers of EDL muscles at 8 days after nerve injury. In soleus muscles, co-expressions of desmin and vimentin were firstly seen in slow-twitch type B fibers at 10 days after nerve injury. Many atrophic fibers, that contained several central nuclei like myotubes and co-expressed desmin and vimentin, were appeared in EDL muscles at 10 days after nerve injury. Although whole regions of fibers were regenerated in EDL muscles, only peripheral regions of fibers were regenerated in soleus muscles at 15 days after nerve injury. Many atrophic fibers, co-expressed of desmin and vimentin, were appeared in EDL muscles at 20 days after nerve injury. These whole fibers represented various degrees of regenerating stages. Most of mature fibers containing several central nuclei, only expressed vimentin slightly, were seen in soleus muscles at 20 days after nerve injury. Most fibers of both muscles were matured at 27 days after nerve injury, but some fibers in EDL muscles were still in processing of degeneration and regeneration. No expressions of desmin and vimentin indicated that muscle fibers were almostly matured in soleus muscles at 27 days after nerve injury. 3) Targetoid or target fibers which informed reinnervation, were appeared firstly in soleus muscles at 20 days and were seen in both muscles at 27 days after nerve injury. All targetoid and target fibers were type B fibers. CONCLUSION: Desmin was revealed in processes of degeneration and regeneration and vimentin was appealed in regeneration process. At the same time, positive immunoreactivity of desmin and vimentin showed specific differences in degree of degeneration and regeneration according to different muscles and muscle fibers.
Animals ; Cytoskeleton ; Desmin ; Intermediate Filament Proteins* ; Intermediate Filaments* ; Laminin ; Leg* ; Mammals ; Muscle Fibers, Skeletal ; Muscle, Striated ; Muscles* ; Myoblasts ; Nerve Crush ; Nerve Fibers, Myelinated ; Nerve Fibers, Unmyelinated ; Rats* ; Regeneration* ; Sciatic Nerve* ; Vimentin

PURPOSE: The intermediate filament proteins, desmin and vimentin, are specific components of the cytoskeleton of striated muscle fibers and of mononuclear cells of mesenchymal origin including myoblasts, respectively. Desmin has also been found in presumptive myoblasts of mammals. The aim of this experiment was attempted to observe the phenotypic changes of intermediate filaments in skeletal muscle fibers during early stages of sciatic nerve crushing injury. MATERIALS AND METHODS: The sciatic nerves of rats were surgically crushed by hemostat and serial cryosections of soleus and extensor digitorum longus(EDL) muscles were prepared at 2, 4, 6, 8, 10, 15, 20 and 27 days after nerve injury. Serial cryosections were immunolabelled with desmin, vimentin and laminin and were histochemically reacted with NADH-TR. RESULTS: 1) Firstly, desmin positive fibers were appeared in fast-twitch type C fibers of both muscles at 6 days after nerve crushing, but were not reacted for vimentin. 2) Co-expressions of desmin and vimentin were firstly detected in fast-twitch type A fibers of EDL muscles at 8 days after nerve injury. In soleus muscles, co-expressions of desmin and vimentin were firstly seen in slow-twitch type B fibers at 10 days after nerve injury. Many atrophic fibers, that contained several central nuclei like myotubes and co-expressed desmin and vimentin, were appeared in EDL muscles at 10 days after nerve injury. Although whole regions of fibers were regenerated in EDL muscles, only peripheral regions of fibers were regenerated in soleus muscles at 15 days after nerve injury. Many atrophic fibers, co-expressed of desmin and vimentin, were appeared in EDL muscles at 20 days after nerve injury. These whole fibers represented various degrees of regenerating stages. Most of mature fibers containing several central nuclei, only expressed vimentin slightly, were seen in soleus muscles at 20 days after nerve injury. Most fibers of both muscles were matured at 27 days after nerve injury, but some fibers in EDL muscles were still in processing of degeneration and regeneration. No expressions of desmin and vimentin indicated that muscle fibers were almostly matured in soleus muscles at 27 days after nerve injury. 3) Targetoid or target fibers which informed reinnervation, were appeared firstly in soleus muscles at 20 days and were seen in both muscles at 27 days after nerve injury. All targetoid and target fibers were type B fibers. CONCLUSION: Desmin was revealed in processes of degeneration and regeneration and vimentin was appealed in regeneration process. At the same time, positive immunoreactivity of desmin and vimentin showed specific differences in degree of degeneration and regeneration according to different muscles and muscle fibers.
Animals ; Cytoskeleton ; Desmin ; Intermediate Filament Proteins* ; Intermediate Filaments* ; Laminin ; Leg* ; Mammals ; Muscle Fibers, Skeletal ; Muscle, Striated ; Muscles* ; Myoblasts ; Nerve Crush ; Nerve Fibers, Myelinated ; Nerve Fibers, Unmyelinated ; Rats* ; Regeneration* ; Sciatic Nerve* ; Vimentin

BACKGROUND: Troponin T(TnT), a 37 kDa polypeptide subunit of contractile protein, is part of the troponin complect in striated muscle, where it binds to tropomyosin. TnT is not usually found in circulating blood, but increase in serum by cytoplasmic damage. Because the amino acid sequence is unique to cardiac muscle, one can immunologically differentiate skeletal muscle and cardiac protein isoforms. METHODS: We evaluated serum cardiac TnT (ELISA, Troponin-T, Boehringer Mannheim, Germany) versos CK-MB mass (IMX CK-MB, Abbott Laboratories, USA) in 46 cases (173 samples) of acute myocardial infarction, 28 cases (94 samples) of ansi na pectoris, 23 cases (62 samples) of other cardiac disease, and 32 cases of non-cardiac disease from September 1994-June 1996. RESULTS: TnT was detected in serum(cutoff value 0.20 ng/ml) within 6 hours after onset of chest pain, slightly earlier than CK-MB mass (cutoff value 5.0 ng/ml). Sensitivity of TnT (81%) is not statistically different from CK-MB mass (84%) within 24 hour of cutest pain but more sensitive after 24-72 hours of symptom, Specificity (79.5%) and positive predictive value (70.7%) of TnT were superior to that of CK-MB mass within 24 fours of cutest pain, and persistent to 6 days, which was longer than that of Cl4-MB mass. More patients show increment of TnT in unstable angina pectoris(40.0%) than stable angina pectoris(15.4%), No difference in detection rate of TnT between angina pectoris(28.6%) and other cardiac disease patients(34.8%). Only 3.1 % of non-cardiac disease patients show TnT increment. CONCLUSIONS: We concluded that TnT Is not detected In most of non-cardiac disease patients, and is an early and later marker with very wide diagnostic time win-dow. Also, TnT can be used as a valuable masker for ischemic myocardial damage in any underlying causes.
Amino Acid Sequence ; Angina, Stable ; Angina, Unstable ; Chest Pain ; Cytoplasm ; Heart Diseases ; Humans ; Muscle, Skeletal ; Muscle, Striated ; Myocardial Infarction* ; Myocardial Ischemia* ; Myocardium ; Protein Isoforms ; Sensitivity and Specificity ; Trinitrotoluene ; Tropomyosin ; Troponin T* ; Troponin*

The aim of this report is to show that treadmill running exercise under well-controlled conditions is to improve of regeneration in rat gastrocnemius muscles after physical injury. For this, rats were submitted to bouts of exercise on a treadmill up a 10 degrees decline for 60 min and gastrocnemius muscles were analysed at different exercise periods by immunohistochemistry in comparison with injured nonexercised muscles. Rats were used with guidelines for experimental procedures as set forth in the Declaration of Helsinki. We analysed the regenerative processes by detection of immunoreactivity for the two intermediate filaments, desmin and vimentin. Desmin and vimentin are specific components of the cytoskeleton of striated muscle fibers and of mononuclear cells of mesenchymal origin including myoblasts, respectively. We found that non-exercised rats had more desmin-and vimentin-positive myofibers than that of exercised rats at 9th, 16th, 23th, 30th day after physical injury. At 30th day, non-exercised rats had several desmin-and vimentinpositive myofibers, but exercised rats had numerous normal myofibers. These results show that exercise is able to improve regeneration processes in physical injured gastrocnemius muscles of rats.
Animals ; Cytoskeleton ; Desmin ; Helsinki Declaration ; Immunohistochemistry ; Intermediate Filaments ; Lower Extremity* ; Muscle, Skeletal ; Muscle, Striated ; Muscles ; Myoblasts ; Rats* ; Regeneration ; Running ; Vimentin

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