A Family of Congenital Fiber Type Disproportion with Mutation in Tropomyosin 3 (TPM3) Gene Presenting as Altered Mentality with Respiratory Distress

Congenital fiber type disproportion (CFTD) has been related with mutations in ACTA1, SEPN1, RYR1 and tropomyosin 3 (TPM3) genes. Particularly, TPM3 mutation was identified as one of the most frequent cause of CFTD and was also detected in cap myopathy and nemaline myopathy. Herein we report patients of autosomal dominant TPM3 missense mutations with CFTD in a Korean family over twogenerations. Two of our patients, who developed mild muscle weakness in infancy, presented with altered mentality and respiratory distress despite relatively mild limb weakness.

Morphological analysis of articularis genus and involvement in muscle synchronicity with vastus intermedius / Análisis morfológico del músculo articular de la rodilla y su participación en la sincronicidad muscular con el músculo vasto intermedio

The articularis genus, which lies under the vastus intermedius, has been regarded as part of the quadriceps femoris. However, they are well known to have different function because their respective origins and insertions are mutually distinct. These muscles are considered to work almost simultaneously when the knee is extended. The electromyogram has been used to demonstrate muscle co-contraction. However, the articularis genus is deeper than other muscles. Moreover, it is difficult to analyze it by surface electromyogram. The relative proportions of muscle fiber types and the characteristics of these fiber types are important determinants of the surface electromyogram. Furthermore, biomechanical analysis of AG has remained unclear. This study investigated the ratio of muscle fiber types in these muscles. Muscle samples from seven human cadaveric specimens were used with application of immunofluorescence double staining. Results show that in the vastus intermedius and articularis genus, the percentage of Type I fibers was significantly higher than that of Type II fibers. No significant difference was found in the mean percentages of Type I and Type II fiber types. The percentages of Type I and Type II fibers in articularis genus muscle were correlated positively to the percentage in the vastus intermedius. These results suggest that similar muscle fiber compositions of these muscles might reflect their contraction during the same active phase of knee extension, despite their different functions.

El músculo articular de la rodilla, que se encuentra cubierto por el músculo vasto intermedio, se ha considerado como parte del músculo cuádriceps femoral. Sin embargo, es sabido que tienen diferentes funciones debido a que sus respectivos orígenes e inserciones son mutuamente distintas. Se considera que estos músculos trabajan de forma casi simultánea cuando la rodilla está extendida. El electromiograma se ha usado para demostrar la contracción muscular. Sin embargo, el músculo articular de la rodillas es más profundo que otros músculos. Además, es difícil analizarlo por electromiograma de superficie. Las proporciones relativas de los tipos de fibras musculares y las características de estos tipos de fibras son importantes determinantes del electromiograma de superficie. Además, el análisis biomecánico de músculo articular de la rodilla no ha sido claro. Este estudio investigó la proporción de tipos de fibras musculares en estos músculos. Se usaron muestras musculares de siete cadáveres humanos con la aplicación de doble tinción de inmunofluorescencia. Los resultados muestran que en los músculos articular de la rodilla y vasto intermedio, el porcentaje de fibras de Tipo I fue significativamente mayor que el de las fibras de Tipo II. No se encontraron diferencias significativas en los porcentajes medios de los Tipo I y Tipo II. Los porcentajes de fibras Tipo I y Tipo II en el músculo articular de la rodilla se correlacionaron positivamente con el porcentaje en el músculo vasto intermediario. Estos resultados sugieren que las composiciones de las fibras musculares similares de estos músculos podrían reflejar su contracción durante la misma fase activa de la extensión de la rodilla, a pesar de sus diferentes funciones.

Progress in the diagnosis and treatment of congenital fiber-type disproportion / 国际儿科学杂志

Congenital fiber-type disproportion (CFTD) is a rare form of congenital myopathy,characterized by non-progressive generalized muscle weakness from early childhood.Diagnosis depends on crucial histological abnormality that type 1 muscle fibers are consistently smaller than type 2 fibers in the absence of other specific histological abnormalities.Whether CFTD should be regarded as a distinct diagnostic entity has always been a controversial issue.Many pathogenic genes have been identified in recent years.This article reviews clinical manifestation,pathology,genetic diagnosis and treatment progress of CFTD.

Preventive effects of endurance exercise on slow-to-fast fiber transition in plantaris muscle of non-obese type 2 diabetic rats / 体力科学

We investigated preventive effects of chronic endurance exercise on the slow-to-fast fiber transition in the plantaris muscles of non-obese type 2 diabetic rats. Eleven-week-old male Spontaneously Diabetic Torii Rats were used as diabetic animals, and assigned to sedentary (DB) and exercise (DB+Ex) groups. Age matched male non-diabetic Sprague-Dawley rats were used as sedentary control (Cnt) group. DB+Ex group was trained on low-intensity treadmill running for 14 weeks. Although glucose level in DB group at 25 weeks of age was higher compared to Cnt group, that in DB+Ex group was significantly lower compared to DB group. DB group exhibited lower percentages of high-oxidative type IIA fibers and higher percentages of low-oxidative type IIB fibers compared to Cnt group in the superficial layer of muscles. While DB+Ex group exhibited higher percentages of type IIA fibers and lower percentages of type IIB fibers compared to DB group in the superficial and deep layers of muscles. Additionally, succinate dehydrogenase intensity in the deep layer of muscles in DB+Ex group was increased by endurance exercise. The present study indicated that endurance exercise could prevent the slow-to-fast fiber transition of the muscle fibers and enhance mitochondrial oxidative enzyme activity in the skeletal muscles of non-obese type 2 diabetic rats.

The Preventive Effects of 8 Weeks of Resistance Training on Glucose Tolerance and Muscle Fiber Type Composition in Zucker Rats

BACKGROUND: We investigated the therapeutic effects of resistance training on Zucker rats before and after the onset of diabetes to understand the importance of the timing of exercise intervention. We assessed whether 8 weeks of resistance training ameliorated impaired glucose tolerance and altered muscle fiber type composition in Zucker rats. METHODS: Five-week-old male Zucker rats were divided into Zucker lean control (ZLC-Con), non-exercised Zucker diabetic fatty (ZDF-Con), and exercised Zucker diabetic fatty (ZDF-Ex) groups. The ZDF-Ex rats climbed a ladder three times a week for 8 weeks. Intraperitoneal glucose tolerance tests (IPGTT) were performed on the 1st and 8th weeks of training, and grip strength was measured during the last week. We also measured glucose transporter 4 (GLUT4) expression by Western blot and immunofluorescence. Moreover, immunohistochemistry was performed to assess muscle fiber type composition. RESULTS: Fasting glucose levels and area under the curve responses to IPGTTs gradually increased as diabetes progressed in the ZDF-Con rats but decreased in the ZDF-Ex rats. Grip strength decreased in the ZDF-Con rats. However, resistance training did not improve grip strength in the ZDF-Ex rats. GLUT4 expression in the ZLC-Con and the ZDF-Con rats did not differ, but it increased in the ZDF-Ex rats. The proportions of myosin heavy chain I and II were lower and higher, respectively, in the ZDF-Con rats compared to the ZLC-Con rats. Muscle fiber type composition did not change in the ZDF-Ex rats. CONCLUSION: Our results suggest that regular resistance training initiated at the onset of diabetes can improve glucose tolerance and GLUT4 expression without changing muscle morphology in Zucker rats.

Muscle fiber type composition, fiber diameter, capillary density in temporalis and masseter muscles and correlation with bite force / Tipos de fibras musculares, diámetro de fibras y densidad capilar en los músculos masetero y temporal y su correlación con la fuerza de mordida

The jaw muscles are essential components in the stomatognatic system. Their complex architecture allows them to execute several motor tasks. One of the structural peculiarities is the presence of hybrid and neonatal fibers.We studied the differences of the fiber-type in masseter and temporalis muscles along the first to nineth decades in both genders. Seventy-four (74) samples were analyzed by immunohistochemistry. Slow and fast muscle fibers distribution was similar in both muscles in both genders. Hybrid fiber was observed in all decades, and its frequency decreased significantly (p<0.001) with aging in masseter. Neonatal myosin expression was observed in all decades, its expression was more frequent in masseter (p=0.01), and males in temporalis (p=0.025). Decrease of the cross sectional area of fast and slow fibers, and decrease of capillary density were detected with aging. These morpho-immunohistochemical alterations on masseter and temporalis muscles correlated to the decrease in bite force with aging.

Los músculos cráneomandibulares son componentes esenciales en el sistema estomatognático. Su arquitectura compleja les permite ejecutar variadas tareas motoras. Una de sus características estructurales es la presencia de fibras musculares híbridas y neonatales. Se estudiaron las diferencias del tipo de fibra en los músculos masetero y temporal en la primera a novena décadas dela vida en ambos sexos. Setenta y cuatro (74) muestras se analizaron por inmunohistoquímica. La distribución de lãs fibras musculares lentas y rápidas fue similar en ambos músculos en ambos sexos. Fibras musculares híbridas fueron observadas en todas las décadas, pero su frecuencia disminuyó significativamente (p <0,001) con el envejecimiento en el masétero. La expresión de miosina neonatal se observo em todas los grupos analizados, aunque su expresión era más frecuente en los músculos maseteros (p = 0,01) y en varones en el temporal (p = 0,025). Se observo una disminución del área de la sección transversal de las fibras rápidas y lentas, y disminución de la densidad capilar al aumentar La edad. Estas alteraciones morfológicas en los músculos masetero y temporal se correlacionan con la disminución de la fuerza asociada al envejecimiento.

Resistance training and protein supplement：Improvement of elderly muscle protein metabolism / 中国组织工程研究

10.3969/j.issn.2095-4344.2013.24.025

O treinamento físico aeróbio corrige a rarefação capilar e as alterações nas proporções dos tipos de fibra muscular esquelética em ratos espontaneamente hipertensos / Aerobic exercise training corrects capillary rarefaction and alterations in proportions of the muscle fibers types in spontaneously hypertensive rats

O treinamento físico (TF) aeróbio tem sido utilizado como um importante tratamento não farmacológico na hipertensão arterial (HA), uma vez que ele reduz a pressão arterial. Estudos mostram que as anormalidades do músculo esquelético na HA estão associados à rarefação capilar, um aumento na porcentagem de fibras de contração rápida (tipo II), com predominância do metabolismo glicolítico e um aumento da fadiga muscular. Entretanto, pouco se conhece sobre os efeitos do TF sobre estes parâmetros na HA. Nós hipotetizamos que o TF corrija a rarefação capilar potencialmente contribuindo para a restauração da proporção dos tipos de fibras musculares. Ratos espontaneamente hipertensos (SHR, n=14) e Wistar Kyoto (WKY, n=14) com 12 semanas de vida e divididos em 4 grupos: SHR, SHR treinado (SHR-T), WKY e WKY treinado (WKY-T) foram estudados. Como esperado, 10 semanas de TF foi efetivo em reduzir a pressão arterial em SHR-T. Além disso, avaliamos os principais marcadores de TF. A bradicardia de repouso, o aumento da tolerância a realização de esforço, do consumo de oxigênio de pico e da atividade da enzima citrato sintase muscular nos grupos de animais treinados (WKY-T e SHR-T) mostram que a condição aeróbia foi alcançada com este TF. O TF também corrigiu a rarefação capilar no músculo sóleo em SHR-T. Em paralelo, foi observada uma redução na porcentagem de fibras do tipo IIA e IIX, ao passo que aumentou a porcentagem de fibras do tipo I induzidas pelo TF na HA. Estes resultados sugerem que o TF previne as alterações na composição dos tipos de fibras no músculo sóleo em SHR, uma vez que a angiogênese e o aumento da atividade da enzima citrato sintase são umas das mais importantes adaptações ao TF aeróbio, atuando na manutenção do metabolismo oxidativo e do perfil de fibras do músculo.

Aerobic exercise training (ET) has been established as an important non-pharmacological treatment of hypertension, since it decreases blood pressure. Studies show that the skeletal muscle abnormalities in hypertension are directly associated with capillary rarefaction, higher percentage of fast-twitch fibers (type II) with glycolytic metabolism predominance and increased muscular fatigue. However, little is known about these parameters in hypertension induced by ET. We hypothesized that ET corrects capillary rarefaction, potentially contributing to the restoration of the proportion of muscle fiber types and metabolic proprieties. Twelve-week old Spontaneously Hypertensive Rats (SHR, n=14) and Wistar Kyoto rats (WKY, n=14) were randomly assigned into 4 groups: SHR, trained SHR (SHR-T), WKY and trained WKY (WKY-T). As expected, ten weeks of ET was effective in reducing blood pressure in SHR-T group. In addition, we analyzed the main markers of ET. Resting bradycardia, increase of exercise tolerance, peak oxygen uptake and citrate synthase enzyme activity in trained groups (WKY-T and SHR-T) showed that the aerobic condition was achieved. ET also corrected the skeletal muscle capillary rarefaction in SHR-T. In parallel, we observed reduction in percentage of type IIA and IIX fibers and simultaneous augmented percentage of type I fibers induced by ET in hypertension. These data suggest that ET prevented changes in soleus fiber type composition in SHR, since angiogenesis and oxidative enzyme activity increased are important adaptations of ET, acting in the maintenance of muscle oxidative metabolism and fiber profile.

Esophageal anatomy of the llama (Lama glama) / Anatomía del esófago de la llama (Lama glama)

This study describes gross, microscopic and muscle fiber anatomy of the esophagus of the llama, Lama glama. The esophagus was studied grossly in twenty-five adult llamas and a subset of ten with normal esophageal physiology was used for the microanatomic studies. Esophageal length was 122 +/- 7 cm with two-thirds of the length in the neck and the remainder in the thorax, consistent with the long neck of the llama. Esophageal diameter increased steadily from 2.5 +/- 0.3 cm in the cranial cervical region to 3.9 +/- 0.8 cm in the caudal thoracic region. The mucosal epithelium was keratinized stratified squamous and there were abundant submucosal glands throughout the esophagus. The entire muscularis of the esophagus was striated muscle in two general layers but also with a somewhat random orientation of fibers. The tunica muscularis steadily increased in thickness from 3.43 +/- 0.30 mm in the cranial cervical region to 4.39 +/- 0.39 mm in the middle thoracic region. In the llama Type 2 muscle fibers predominated in the esophageal musculature, with the percentage of Type 1 fibers increasing from 1 percent cranially to 33 percent in the caudal thoracic region of the esophagus. This study of the normal llama esophagus enhances our knowledge of this species and provides the basis for future study of pathological conditions of the esophagus.

Este estudio describe la anatomía morfológica, microscópica, y tipo de fibra muscular del esófago de la llama, Lama glama. Estudiamos la anatomía morfológica del esófago, con fisiología normal, en 25 llamas adultas y, adicionalmente, en 10 de ellas la anatomía microscópica. La longitud del esófago fue 122 +/- 7 cm con dos tercios en el cuello y un tercio en el tórax. El diámetro del esófago aumentó de 2,5 +/- 0,3 cm en la región craneal del cuello y a 3,9 +/- 0,8 cm en la región caudal del tórax. El epitelio de la mucosa eera escamoso estratificado queratinizado y la submucosa contenía abundantes glándulas a lo largo de todo el esófago. La muscular entera del esófago se compuso de músculo esquelético en más o menos dos capas, pero con algunas fibras orientadas al azar. La muscular aumentó de 3,43 +/- 0,30 mm en la región craneal del cuello a 4,39 +/- 0,39 mm en la región media del tórax. Fibras musculares Tipo 2 predominaron en la muscular. El porcentaje de fibras Tipo 1 aumentó de 1 por ciento al inicio del esófago a 33 por ciento en la región caudal torácica. Este estudio del esófago normal de la llama ofrece más información sobre la anatomía de la llama y proporciona una base para futuros estudios de patologías esofágicas.

A Case of Congenital Fiber Type Disproportion with Multiple Anomalies / 대한소아신경학회지

Congenital fiber type disproportion (CFTD) is a rare form of congenital myopathy characterized by the smallness and the marked predominance of type 1 fibers, which presents congenital hypotonia, delayed motor milestones, joint contractures, and skeletal deformities. The muscle biopsy reveals the type 1 fibers are more than 12% smaller than the type 2 fibers in size. We describe a 24-month-old boy who presented muscle hypotonia, delayed motor milestones, mental retardation with generalized tonic clonic seizures, and the muscle pathologic findings of CFTD. Additional findings included left cryptorchidism, congenital subluxation of the hip, contractures of ankle joints, diffuse brain atrophy, and optic nerve atrophy. We should consider CFTD as a differential diagnosis of early onset myopathy.

CHANGES IN SARCOPLASMIC RETICULUM Ca²⁺-SEQUESTERING CAPACITY DURING RECOVERY FOLLOWING HIGH-INTENSITY EXERCISE / 体力科学

The purpose of this study was to investigate changes in sarcoplasmic reticulum (SR) Ca²⁺-sequestering capacity in rat fast-twitch plantaris (PL) and slow-twitch soleus (SOL) muscles during recovery after high-intensity exercise. The rats were subjected to treadmill runs to exhaustion at the intensity (10% incline at 50 m/min) estimated to require 100% of maximal O₂ consumption. The muscles were excised immediately after exercise, and 15, 30 and 60 min after exercise. Acute high-intensity exercise evoked a 27 % and 38 % depression (<i>P</i><0.05) in SR Ca²⁺-uptake rate in the PL and SOL, respectively. In the PL, uptake rate remained lower (<i>P</i><0.05) at 30 min of recovery but recovered 60 min after exercise. These alterations were paralleled by those of SR Ca²⁺-ATPase activity. On the other hand, SR Ca²⁺-uptake rate in the SOL recovered 15 min after exercise. Unlike the PL, discordant time-course changes between SR Ca²⁺-ATPase activity and uptake occurred in the SOL during recovery. SR Ca²⁺-ATPase activities were unaltered with exercise and elevated (<i>P</i><0.05) by 25, 30 and 30% at 15, 30 and 60 min of recovery, respectively. These results demonstrate that SR Ca²⁺-sequestering ability is restored faster in slow-twitch than in fast-twitch muscle during recovery periods following a single bout of high-intensity exercise and suggest that the rapid restoration of SR Ca²⁺-sequestering ability in slow-twitch muscle could contribute to inhibition of disturbances in contractile and structural properties that are known to occur with raised myoplasmic Ca²⁺ concentrations.

Comparison of Clinical Characteristics Between Congenital Fiber Type Disproportion Myopathy and Congenital Myopathy with Type 1 Fiber Predominance

Congenital myopathies are clinical and genetic heterogeneous disorders characterized by skeletal muscle weakness and specific structural changes in muscle fiber. Congenital myopathy with fiber type disproportion (CFTD) is an established disorder of congenital myopathy. CFTD is characterized by non-progressive childhood neuromuscular disorders with a relatively good prognosis and type 1 fiber predominance and smallness. Congenital myopathy with type 1 fiber predominance (CMT1P) is also a distinct entity of congenital myopathy characterized by non-progressive childhood neuromuscular disorders and type 1 fiber predominance without smallness. Little is known about CMT1P. Clinical characteristics, including dysmorphic features such as hip dislocation, kyphoscoliosis, contracture, and high arch palate, were analyzed along with laboratory and muscle pathologies in six patients with CMT1P and three patients with CFTD. The clinical manifestations of CFTD and CMT1P were similar. However, the frequency of dysmorphic features is less in CMT1P than in CFTD. Long term observational studies of CMT1P are needed to determine if it will change to another form of congenital myopathy or if CMT1P is a distinct clinical entity.

Effect of exercise on muscle fiber type transform / 基础医学与临床

Fiber type of skeletal muscle and its multiple and specialized protein isoform are the structure and molecular basis of the skeletal muscle's function and adaptability.Myosin heavy chain(MHC)isoform,as the factor determinating the type of the skeletal muscle to be fast or slow one,has become molecular biomarker of muscle fiber type and adaptability.Exercise may lead to the transform between myosin subtypes.This article reviewed not only the relation between myosin heavy chain and muscle fiber type of skeletal muscle,but also the influences of different motor patterns' on the transform of skeletal muscle fiber MHC isoform.

A Case of Congenital Fiber Type Disproportion Associated with External Ophthalmoplegia

Congenital fiber type disproportion (CFTD) is a form of congenital myopathy characterized by histologic findings of the smallness of type 1 fiber and type 1 fiber predominance. It is usually associated with hypotonia and motor weakness of the limb muscles at birth or the neonatal period. We report a 6-year-old girl with limb weakness and ophthalmoplegia, whose muscle pathology showed the classic pattern of CFTD without any other abnormality.

Transneuronal Degeneration Due to Peripheral Nerve Injury in the Rats / 체질인류학회지

When an axon is severed, degenerative changes occur in the injured neuron as well as in those with which it has synaptic connections through transneuronal degeneration. Transneuronal degeneration includes all atrophic or degenerative changes that occur in nerve cells following the disappearance of their efferent (retrograde transneuronal degeneration) or afferent (anterograde transneuronal degeneration) connections. Previous studies have shown that transneuronal degeneration may occur in the neurons of various central nervous system following injury to their peripheral nerve. However, the effect of transneuronal degeneration on the neurons which are related with damaged neurons functionally and structurally is not elucidated yet. Denervation due to axonal degeneration or dysfunction of nerve cell bodies leads to physiological and biochemical changes in the skeletal muscles, and the extent of neuronal degeneration can be assessed through the muscle atrophy and the changes in muscle fiber type density. In order to identify the effect of transneuronal degeneration on the adjacent peripheral nerves as well as muscles, the left femoral nerve of Sprague -Dawley rats was transected, and changes in their spinal cords and hindlimb muscles were analysed morphologically and histochemically. The results obtained are as follows : 1. the motor neurons of ipsilateral anterior horn of femoral nerve transected rats showed reduction in size and degenerative features such as shriven shape and nucleus moved to periphery of the cell body. 2. All three muscle fiber types of rectus femoris and adductor longus were reduced in muscle fiber size, but no such changes were observed in semitendinosus. 3. In rectus femoris and adductor longus, type IIa muscle fiber was increased in number and the number of type IIb fiber was reduced, whereas no change was observed in all three muscle fiber types of semitendinosus. These findings indicate that damaged neurons following peripheral nerve injury can affect other adjacent neurons through transneuronal degeneration and cause the denervative changes in the muscles innervated by those adjacent neurons concomitantly, and such effects are only observed in the same spinal cord level.

Dynamic graciloplasty for canine in situ anal reconstruction / 中国普通外科杂志

Objective To evaluate dynamic graciloplasty (DGP) for canine in situ anal reconstruction. Methods Seventeen dogs were randomly divided into experimental group and control group. In control group, on the stage 1, the gracilis muscle were dissected in situ, manometry performed intraoperatively; In experimental group, the gracilis muscle were dissected in situ and stimulated chronically starting 7 days postoperatively. On stage 2, abdominoperineal resection of anus and graciloplasty for anal reconstruction were performed in two groups. After 2 weeks recovery, manometry and muscular fatigue-resistant curve (MFRC) were observed while myostimulator is switched off and on. The muscle of neosphincter was biopsied. Results After chronic low frequency electrical stimulation (CLFS), the percentage of type Ⅰ fibers in the stimulation group was higher than the control group (P0.05), but functioning neosphincter pressure is different significantly (P

Muscle fiber type disproportion with an autosomal dominant inheritance

Congenital muscle fiber type disproportion (CFTD) has been described as a form of congenital myopathy characterized by the smallness and marked predominance of type 1 fibers in a muscle biopsy. Clinical manifestations include hypotonia, nonprogressive muscle weakness, joint contractures, and skeletal deformities. However, it has also been noted that the same pathologic alterations appeared in clinically diverse conditions. Recently, we experienced a family, a mother and two children, in which a muscle biopsy showed the mother to have muscle fiber type disproportion. This case was unusual in that there was a significant progression of weakness, an absence of neonatal hypotonia, and other commonly associated musculo-skeletal deformities. In this report, we describe the clinicopathologic features of the family with a brief review about muscle fiber type disproportion.

Congenital Fiber Type Disproportion Myopathy: A case report

Authors report a typical case of congenital fiber type disproportion (CFTD) with unique clinicopathologic characteristics. The patient was a 13-year-old boy who presented with weakness of lower extremities, especially proximal muscle, since his infancy. He has suffered from severe scoliosis which got worse since the age of 12. He showed mild dysarthria, high arched palate, and fish face. All routine laboratory data were within normal limits. EMG findings suggested myopathy. The muscle biopsy revealed fiber type disproportion with type 1 predominance. While most of the type 1 myofibers were atrophic or normal in size, the type 2 fibers showed universal hypertrophy. The difference of mean diameter between the larger and the smaller fibers was 27.9%. The patient's clinicopathologic settings fulfilled the criteria of CFTD.

Fiber type specific distribution of stress proteins in rat skeletal muscle / 体力科学

To determine whether fiber type-specific expression of heat shock protein (HSP, or stress protein) occurs in unstressed rat skeletal muscle, the medial gastrocnemius of adult female Sprague-Dawley rats was subjected to immunohistochemical analysis. Antibodies against 5 types of anti-myosin heavy chain (MHC) were used to classify the type of fibers, and 2 types of anti-HSP antibodies were employed to analyze the fiber type-specific expression.<BR>Serial cross-sections of 10 μm thick cut by a cryostat were incubated with primary anti-MHC or anti-HSP 60 and 72 antibodies, followed by biotinylated secondary anti-mouse antibodies, and avidin-biotin complex solution. A peroxidase DAB substrate kit (Vector SK-4100) or BCIP/NBT solution was used to visualize the immunoreaction of each fiber type.<BR>By using the 5 types of anti-MHC antibodies, fibers were classified into 4 types : slow-type I, fasttypes IIA, IIX, and IIB. Anti-HSP 72 antibody reacted with many, but not all, type I and IIA fibers, whereas anti-HSP 60 antibody reacted specifically with type I fibers. Neither type IIX nor IIB fibers showed immunoreactivity with anti-HSP 60 or 72 antibodies. These results suggest that the expression of HSP 60 protein is related to that of type I MHC, and that the expression of HSP 72 protein may be related to that of types I and ha MHC, in unstressed rat skeletal muscle.

Changes in contractile properties, fiber type and myosin heavy chain isoform compositions of rat skeletal muscle induced by chronic overload / 体力科学

The effects of chronic overload by synergist ablation (SA) on fiber type, myosin heavy chain (MyoHC) isoforms, and contractile properties in the rat plantaris muscle were studied. Plantaris muscle was overloaded by bilateral removal of its synergist of gastrocnemius muscle in Fischer 344 female rats (aged 8 weeks) . Muscles of sham-operated legs served as controls.<BR>The overloaded plantaris was 20% heavier than control 3 weeks after SA. Overload by SA resulted in remarkable increases in cross-sectional areas of muscle fibers of all types ; however, the percentage increase was less in type II b fibers. Twitch contraction and half-relaxation time before and after tetanus did not change, but fatigue resistance increased significantly with overload. The percentage of area occupied by type II b fibers, which have lower oxidative capacity, decreased while the percentage of area occupied by other type II fibers, but not type I fibers, increased. Analysis of MyoHC isoforms with gradient sodium dodecylsulfate polyacrylamide gel electrophoresis revealed a decrease in II b isoforms and an increase in II d isoforms.<BR>These results suggest that chronic overload produces changes in muscle fiber type and MyoHC isoform compositions which partly account for increased fatigue resistance in overloaded muscles.