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At least 469 records · Page 26Linked to original sources
PubMed1999

In vivo analysis of two striated muscle actin promoters reveals combinations of multiple regulatory modules required for skeletal and cardiac muscle-specific gene expression.

We isolated two striated muscle actin genes from medaka Oryzias latipes. OIMA1 is a skeletal muscle actin gene expressed in somitic muscle and head muscle and OIMA2 is probably a cardiac muscle actin gene expressed in both somitic and cardiac muscle. The differential transcription mechanisms for these two genes were examined in embryos by introducing fusion genes in which the OIMA1 or OIMA2 upstream region was connected to the green fluorescent protein gene. Embryos were injected with these fusion genes at the 2-cell stage. A fusion gene containing the region up to -949 of OIMA1 exhibited strong expression in somitic muscle. The coexistence of two regions, -949/-662 and -421/-201, is necessary for skeletal muscle-specific expression of OIMA1. Two E boxes and other unidentified sequences cooperatively function to achieve the full activity of the enhancer -949/-662. As for OIMA2, the region up to -520 is sufficient for strong muscle-specific expression. The region between -520 and -174 of OIMA2 is necessary for specific expression in both skeletal and cardiac muscles. In addition to the CArG box located at -140, an E-box at -430 is important for the expression in cardiac muscle as well as skeletal muscle. When the enhancers for the two muscle actin genes were switched and combined with each other's promoter, they were able to upregulate tissue-specific expression according to their origin. These results suggest that distinct expression patterns of OIMA land OIMA2 are regulated by combination of regulatory modules, each of which contains multiple regulatory elements.

Actins↗
PubMed2003

Regulation of insulin-like growth factor-I in skeletal muscle and muscle cells.

Growth hormone (GH) and insulin-like growth factor-I (IGF-I) are potent regulators of muscle mass. Transgenic mice that over-express these proteins exhibit dramatically enlarged skeletal muscles. In contrast, malnutrition, critical illness, sepsis, and aging are all associated with a dramatic reduction in muscle mass and function. The circulating concentration of IGF-I and the expression of IGF-I in skeletal muscle are also reduced during catabolic states. Consequently, GH has been used clinically to increase lean body mass in patients with muscle wasting. Likewise, delivery of IGF-I specifically into muscle has been proposed as a genetic therapy for muscle disorders. A better understanding of the regulation of IGF-I expression in skeletal muscle and muscle cells is therefore of importance. Yet, our knowledge in this area has been limited by a lack of GH responsive muscle cells. In addition the IGF-I gene spans over 90 kb of genomic DNA and it exhibits a very complex regulatory pattern. This review will summarize our knowledge of the control of muscle mass by GH, IGF-I, anabolic steroids, exercise and other growth enhancing hormones. We will also highlight recent advances in the regulation of IGF-I and signal transducers and activators of transcription (Stats) by GH. A special emphasis will be placed on the interaction of IGF-I and proinflammatory cytokines in skeletal muscle and muscle cells.

Anabolic Agents↗
PubMedDate not supplied

[Plasticity of allogenic muscle tissue transplanted into a traumatized rat muscle subjected He-Ne laser radiation].

The effect of muscle tissue alloplasty and laser radiation on the post-traumatic regeneration of skeletal muscles was studied. The implantation of an unirradiated minced allogenic muscle tissue into the area of trauma of a previously laser-irradiated muscle had a positive effect. The allogenic muscle tissue underwent active regeneration. The traumatized muscle fibers in the rat-recipient muscle grew into the alloplant. The implantation of a previously laser-irradiated muscle tissue into the area of trauma of an unirradiated muscle was less effective. The allogenic muscle tissue prevented the growth of rat-recipient myofibers and underwent lysis in general. The allotransplantation of a laser-irradiated muscle tissue into an x-irradiated (20 Gy) traumatized muscle increased the destruction of rat-recipient muscle tissue.

Animals↗
PubMed1990

[Muscle regeneration in mdx mouse, and a trial of normal myoblast transfer into regenerating dystrophic muscle].

The most ideal therapeutic trial on Duchenne muscular dystrophy (DMD) is a transfer of normal myoblasts into dystrophic muscle which has been attempted on animal models in several institutes. In the process of muscle regeneration, the transferred normal myoblasts are expected to incorporate into the regenerating fibers in host dystrophic mouse. To know the capacity of muscle regeneration in dystrophic muscle, we compared the regenerating process of the normal muscle with that of the dystrophic muscle after myonecrosis induced by 0.25% bupivacaine hydrochloride (BPVC) chronologically. In the present study, C57BL/10ScSn-mdx (mdx) mouse was used as an animal model of DMD and C57BL/10ScSn (B10) mouse as a control. There was no definite difference in the behavior of muscle fiber regeneration between normal and dystrophic muscles. The dystrophic muscle regenerated rapidly at the similar tempo to the normal as to their size and fiber type differentiation. The variation in fiber size diameter of dystrophic muscle, however, was more obvious than that of normal. To promote successful myoblast transfer from B10 mouse into dystrophic mdx mouse at higher ratio, cultured normal myoblasts were transferred into the regenerating dystrophic muscle on the first and the second day after myonecrosis induced by BPVC. Two weeks after the myoblast injection, the muscles were examined with immunohistochemical stain using anti dystrophin antibody. Although dystrophin-positive fibers appeared in dystrophic muscle, the positive fibers were unexpectedly small in number (3.86 +/- 1.50%).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

Lysosomal changes in skeletal muscles during the repair of exercise injuries in muscle fibers.

Lysosomal changes were recorded in the skeletal muscles of mice and rats during the repair of muscle fiber injuries caused by a single bout of prolonged running. One purpose of the study was to characterize cellular and compartmental distributions of lysosomal enzymes and to investigate ultrastructural changes in the lysosomal system associated with the appearance and repair of muscle fiber injuries. Furthermore, the level of muscle fiber injuries was correlated with the lysosomal enzyme response and the indices obtained were utilized in the evaluation of the pathogenesis of exercise myopathy. The main results were: Heavy physical exertion caused scattered necrotic injuries of muscle fibers and inflammation in several skeletal muscles. The most susceptible muscles to exercise injuries were the red deep parts of quadriceps femoris muscle and the soleus and tibialis anterior muscles. The total activities of several lysosomal acid hydrolases, in particular those of beta/-glucuronidase, cathepsin C and arylsulphatase, strongly increased during the repair of exercise injuries. The highest responses occurred 3-5 days after exertion and the degree of enzyme responses correlated significantly with the level of histological injuries. The histochemical staining intensities of beta-N-acetylglucosaminidase and beta-glucuronidase were highest 3 and 5 days after exertion. An increased staining intensity occurred in the inflammatory phagocytes and in the surviving muscle fibers, especially in the red muscle fibers close to necrotic foci. An autophagic response occurred in the muscle fibers close to necrotic foci 2-7 days after exertion. Autophagic vacuoles were frequently small and contained different cellular structures at various stages of degradation. The number of lysosome-like bodies, Golgi complexes and multilamellar bodies also increased. Macrophages removed the debris of necrotic muscle fibers by heterophagic uptake 2-5 days after exertion. The unsedimentable and releasable activities of acid hydrolases increased more prominently than those of the total activities in homogenates and reached their highest values 3 days after exertion. The proportional distribution of various acid hydrolases to unsedimentable, releasable and bound fractions varied strikingly but remained appreciably stable throughout the exercise myopathy. The content of lysosomal phosphomannosyl-enzyme receptors in the membrane fraction was unchanged 0-3 days after exertion but a small increase occurred later. The endogenous receptor-bound activity of beta-N-acetylglucosaminidase was considerably increased 1-5 days after exertion but decreased later to the control level.(ABSTRACT TRUNCATED AT 400 WORDS)

Age Factors↗
PubMed1988

Inosine and adenosine formation in ischemic and non-ischemic contracting muscles of rats: difference between fast and slow muscles.

Inosine and adenosine formation was evaluated in different types of rat skeletal muscle during ischemic and non-ischemic contraction. Extensor digitorum longus (EDL, fast) and soleus (slow) muscles were stimulated electrically via the sciatic nerve (5 Hz, 10 min). Under non-ischemic condition, the concentrations of IMP, inosine, adenosine, and hypoxanthine increased in EDL muscles but not in soleus muscles during stimulation. Under ischemic condition, these metabolites increased in both EDL and soleus muscles, although the increases in IMP and inosine were greater in EDL muscles. The increase in inosine had a strong positive correlation with that in IMP in ischemic EDL and soleus muscles, but the ratio, delta inosine/delta IMP was smaller in EDL muscles. The increase in adenosine under ischemic condition was not significantly different between the two muscles. These findings suggest that ischemia enhances degradation of purine nucleotides in contracting fast and slow muscles, and that although the degradation of purine nucleotides to IMP is greater in fast muscles than in slow muscles, the relative degradation rate of IMP to inosine is rather smaller in fast muscles.

Adenosine↗
PubMed1986

Pattern of skeletal muscle regeneration after reautotransplantation of regenerated muscle.

Autotransplantation of rat extensor digitorum longus muscle results in initial myofibre degeneration and subsequent regeneration from precursor myosatellite cells. To determine what effect a reinjury would have on the regenerative response, in the present study, once transplanted and regenerated muscles were reinjured by reautotransplantation. In rats, four weeks after initial transplantation, when the regeneration was complete, the extensor digitorum longus muscle was transplanted again and the pattern of regeneration in reautotransplanted and once autotransplanted muscles was compared. Muscles were analysed 2, 4, 7, 14 and 30 days after autotransplantation and reautotransplantation. Both autotransplanted and reautotransplanted muscles underwent degeneration and regeneration; however, the pattern of regeneration in these two transplants was quite different. In autotransplants, a thin myogenic zone, marked by activated myoblasts, was first seen at 4 days. By 7 days the width of myogenic zone increased but still many degenerating myofibres were present in the central region of the muscle. By 14 days the muscle was filled with regenerated myotubes and myofibres. The reautotransplanted muscles underwent similar regenerative events; however, the rate of regeneration was considerably faster. The myogenic zone was apparent as early as 2 days and was much larger at 4 days, and by 7 days the entire muscle was filled with regenerated myotubes and myofibres which matured at later time intervals. Furthermore, the decrease in muscle weight in reautotransplanted muscles was not as much as that seen after autotransplantation. These findings reveal that not only is skeletal muscle capable of regeneration after a second injury, but the rate of this regeneration is much faster. This increased rate and recovery may be due to a conditioning effect of the first injury.

Animals↗
PubMed1995

Alteration of regulatory enzyme activities in fast-twitch and slow-twitch muscles and muscle fibres in low-intensity endurance-trained rats.

The effect of progressive, low-intensity endurance training on regulatory enzyme activities in slow-twitch (ST) and fast-twitch (FT) muscle fibres was studied in 32 rats. Of those rats 16 were trained on a treadmill at a running speed of 10 m.min-1 5 days a week over an 8-week period. Running time was progressively increased from 15 min to 2 h.day-1. Of the rats 4 trained and 4 sedentary rats were also subjected to acute exhausting exercise. Enzyme activities of phosphofructokinase 1 (PFK1) from glycolysis, alpha-ketoglutarate dehydrogenase (alpha-KGDH) from the Krebs cycle and carnitine palmitoyltransferase (CPT I and II) from fatty acid metabolism in soleus, tibialis anterior and gastrocnemius muscles were measured in trained and sedentary rats. Enzyme activities of individual ST and FT fibres were measured from the freeze-dried gastrocnemius muscle of 8 trained and 8 sedentary rats. In the sedentary rats the activity of PFK1 in tibialis anterior and soleus muscles was 141% and 41% of the activity in gastrocnemius muscle, respectively. The activity of alpha-KGDH in tibialis anterior and soleus muscles was 164% and 278% of the activity in gastrocnemius muscle, respectively. The activity of CPT I in tibialis anterior and gastrocnemius muscles were at the same level, but in soleus muscle the activity was 127% of that in mixed muscle. Endurance training increased enzyme activities of alpha-KGDH and CPT I significantly (P < 0.05) in gastrocnemius muscle but not in soleus or tibialis anterior muscle.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1998

Feline caudofemoralis muscle. Muscle fibre properties, architecture, and motor innervation.

Feline caudofemoralis (CF) is a promising preparation in which to study the properties of mammalian fast-twitch skeletal muscle, but little is known about its muscle fiber properties, architecture, and motor innervation. We used histochemical techniques to confirm that it contained predominantly type IIB fibers (95+/-2%, n=8, with six of eight muscles composed exclusively of type IIA and IIB fibers), but physiological experiments showed less fatiguability than for the type IIB component of medial gastrocnemius. This may be related to the surprisingly strong and regular recruitment of CF during repetitive tasks such as walking and trotting, which we demonstrated electromyographically. We measured muscle length over the anatomical range of motion for CF (approximately 0.6-1.2 L0) and estimated working length during walking and trotting (approximately 0.95-1.15 L0). The specific tension was similar to that of the exclusively slow-twitch soleus muscle (31.2+/-4.7 N/cm2 compared with 31.8+/-4.1 N/cm2; P>0.8). Single fiber dissections of CF revealed a series-fibered architecture with a mean of 2.3 fibers, each 2.5 cm long, required to span the fascicle length. We identified two neuromuscular compartments in CF by cutting one of the two nerve branches innervating CF and depleting the glycogen stores in the intact motor units. These compartments were in parallel and extended the length of the muscle; their electromyographic activity was similar during various natural behaviors. CF and gluteus maximus motoneurons were labeled concurrently with a combination of fluorescent, retrograde tracers including Fluororuby, Fluorogold and Fast Blue. The CF motor nucleus was located in L7-S1, overlapping and intermingling extensively with the nucleus of the adjacent gluteus maximus muscle. Distributions of CF motoneuron diameter revealed one large peak around 50-55 microm, with relatively few small-diameter (less than 35 microm) cells. Using estimates of the total number of fibers in three muscles and the estimated number of alpha-motoneurons for those same muscles, we calculated a mean innervation ratio of approximately 270, which is at the low end of the innervation ratios for type IIB motor units from other feline muscles and more similar to type IIA motor units. In general, CF appears to be a useful preparation in which to study the properties of fast-twitch muscle, but these properties may vary somewhat from type IIB fibers from different muscles.

Acetylcholinesterase↗
PubMed1978

Turnover of muscle protein in the fowl (Gallus domesticus). Rates of protein synthesis in fast and slow skeletal, cardiac and smooth muscle of the adult fowl.

Rates of protein synthesis in skeletal, cardiac and smooth muscle of fully grown fowl (Gallus domesticus) were determined in vivo by means of the constant infusion method using [14C]proline. In the anterior latissimus dorsi muscle, containing predominantly slow fibres, the average synthesis rate of non-collagen muscle proteins was 17.0 +/- 3.1% per day, a value higher than that obtained for cardiac muscle (13.8 +/- 1.3% per day) and for smooth muscle of the gizzard (12.0 +/- 1.9% per day). In the posterior latissimus dorsi muscle, containing predominantly fast fibres, synthesis rates were much lower (6.9 +/- 1.8% per day). In each case these average rates for the non-collagen protein were similar to the average rate for the sarcoplasmic and myofibrillar protein fractions. The RNA concentration of these four muscles showed that relative rates of protein synthesis were determined mainly by the relative RNA concentrations. The rate of protein synthesis per unit of DNA (the DNA activity) was similar in the two skeletal muscles, but somewhat lower in cardiac muscle and gizzard, possibly reflecting the larger proportion of less active cell types in these two muscles. These quantitative aspects of protein turnover in the two skeletal muscles are discussed in terms of the determination of ultimate size of the DNA unit, and in relation to muscle ultrastructure.

Animals↗
PubMed2001

Cerebral palsy in adults: Independent effects of muscle strength and muscle tone.

OBJECTIVE: To investigate clinical characteristics and their contribution to activities of daily living (ADLs) in adults with cerebral palsy (CP). DESIGN: Descriptions of the clinical features of medical disorders; survey. SETTING: Rehabilitation counseling center in Japan. PATIENTS: A case series of 256 patients (140 men, 116 women; mean age, 31.6yr; range, 17-83yr) admitted to a rehabilitation center from January 1995 to December 1997. MAIN OUTCOME MEASURES: Characteristics investigated included severity of mental retardation, topography of motor deficits, motor power by manual muscle testing, muscle tone rated by using the muscle tone scale, deformity, sensory disturbance, and pain. ADLs were evaluated with the Barthel Index. RESULTS: Patients showed severe impairment in terms of the Ashworth scale for grading spasticity and deformity, and moderate impairment on manual muscle testing. ADLs were influenced significantly by topography of motor deficits, manual muscle test scores, and muscle tone scale assessment (p <.0001). The muscle tone scale findings showed a significant correlation with deformity (p <.0001), but did not correlate with manual muscle testing. ADLs were affected by muscle power and muscle tone independently. CONCLUSION: Adults with CP showed markedly increased muscle tone and moderate muscle weakness. These 2 factors did not correlate with each other, and were independently responsible for worse ADLs.

Activities of Daily Living↗
PubMed1975

The effects of muscle cooling and stretch on muscle spindle secondary endings in the cat.

1. The objectives of the investigation were to identify the muscle spindle endings which respond to cooling of the relaxed muscle and to study their response to stretch. 2. The discharge of single afferents from 162 de-efferented muscle spindles in the relaxed medial gastrocnemius muscle of the anaesthetized cat was studied in vivo during cooling of the muscle from 37 to 24 degrees C. Temperature measurements were made at the inner surface of the muscle, while cooling (never below 15 degrees C) was applied at the skin over the muscle. 3. The endings were classified as primary or secondary endings on the basis of their conduction velocity, the dividing line being set at 70 m/sec. A response to cooling was obtained only from endings with afferents conducting at velocities of 20-70 m/sec. These fifty-six endings (CR) represented 65% of the secondary endings studied; the remaining secondary endings (NCR) and the primary endings showed no activity during cooling of the relaxed muscle. 4. During maintained stretches of 4-12 mm, activity of the NCR and primary endings decreased when the muscle was cooled. Cooling affected the CR endings in the same way, but only if the muscle was stretched 6 mm or more. During a smaller maintained muscle stretch, cooling caused an increase in CR activity, superimposed on the response to stretch. 5. The response to a 10 mm stretch at velocities of 10-70 mm/sec was studied in twenty-six CR, eleven NCR and twenty-one primary endings. 6. The dynamic responses of CR endings were intermediate between those of the primary endings and NCR endings. For any velocity of stretch the mean dynamic index of the CR endings was significantly greater than that of the NCR endings but significantly less than that of the primary endings. 7. The mean static responses of the CR and primary endings, measured 0-5 sec after the end of ramp stretch, were the same and significantly greater than that of the NCR endings. 8. The results indicate that cooling of the relaxed mammalian muscle may be used to differentiate between primary endings and about two-thirds of the secondary endings. The remaining secondary endings can be recognized by their small dynamic and static response to stretch.

Action Potentials↗
PubMed1995

Injury to muscle fibres after single stretches of passive and maximally stimulated muscles in mice.

1. Our purpose was to investigate the initial mechanisms responsible for contraction-induced injury. Most studies of mechanisms of contraction-induced injury have been based on observations made either shortly after many repeated contractions at the peak of fatigue, or days after, at the peak of delayed onset injury. As a result, conclusions based on these studies are complicated by interactions of mechanical and biochemical events, as well as the passage of time. We studied the initial mechanical events associated with contraction-induced injury immediately following single stretches of whole skeletal muscles of mice in situ. 2. We tested the hypothesis that immediately following a single stretch, the severity of contraction-induced injury is a function of both strain and average force. Consequently, the work done to stretch the muscle would be the best predictor of the magnitude of injury. Extensor digitorum longus muscles were adjusted to optimum length for force (L(o)). Passive (not stimulated) and maximally activated muscles were exposed to single stretches of 10, 20, 30, 50 or 60% strain, relative to muscle fibre length (Lf), at a rate of 2 Lf s-1. 3. The magnitude of injury was represented by the force deficit 1 min after the stretch expressed as a percentage of the maximum force prior to the stretch. The occurrence of injury was confirmed directly by electron microscopic analysis of the ultrastructure of muscle fibres that were fixed immediately following single stretches. 4. For active muscles, a single stretch of only 30% strain produced a significant force deficit, whereas for passive muscles, a larger strain was required. Stretches of greater than 50% strain resulted in greater force deficits for passive than for maximally activated muscles. For either condition, the work done to stretch the muscle was the best predictor of the magnitude of injury, accounting for 76% of the variability in the force deficit for maximally activated muscles, and 85% for passive muscles.

Animals↗
PubMed2001

A muscle precursor cell-dependent pathway contributes to muscle growth after atrophy.

Slow-twitch skeletal muscle atrophies greatly in response to unloading conditions. The cellular mechanisms that contribute to the restoration of muscle mass after atrophy are largely unknown. Here, we show that atrophy of the mouse soleus is associated with a 36% decrease in myonuclear number after 2 wk of hindlimb suspension. Myonuclear number is restored to control values during the 2-wk recovery period in which muscle mass returns to normal, suggesting that muscle precursor cells proliferate and fuse with myofibers. Inhibition of muscle precursor cell proliferation by local gamma-irradiation of the hindlimb completely prevents this increase in myonuclear number. Muscle growth occurs normally during the first week in irradiated muscles, but growth during the second week is inhibited, leading to a 50% attenuation in the restoration of muscle mass. Thus early muscle growth occurs independently of an increase in myonuclear number, whereas later growth requires proliferating muscle precursor cells leading to myonuclear accretion. These results suggest that increasing the proliferative capacity of muscle precursor cells may enhance restoration of muscle mass after atrophy.

Animals↗
PubMed1997

Spindle representation relative to distribution of muscle fiber types in the cat capsularis muscle.

The spatial representation of muscle spindles (Sps) in the small (approximately 0.2 g), simply structured capsularis muscle that crosses anterior to the cat's hip joint was compared with the distribution of the slow oxidative (SO) and few (< 10%) fast oxidative-glycolytic (FOG) fibers of which it is composed to see if their distributions were consistent with a hypothesis that sensory input from Sps influences the incidence of extrafusal fiber types. In frozen sections from 4 muscles, FOG fibers were enumerated along 1-mm strips across the muscle's maximum width, and between the 'superficial' surface and the 'deep' one that contacts the joint. The locations of Sps in complete serial sections of 2 paraffin-embedded muscles, one perfused with the hip joint flexed and the other with it extended, were plotted on an outline of each muscle at its midlength, and their numbers and density in horizontal and sagittal 'strata' determined. In general, the incidence of Sps increased down the superficial-to-deep axis, while FOG fibers became fewer, as is consistent with support of SO status by Sp input. Along the craniocaudal axis, i.e. width, the numbers of FOG fibers rose toward the hip joint, but this was not associated with a monomodal gradient of Sps. In the extended muscle, however, the lengths of the axial bundle and capsular space of Sps in the half of the muscle next to the joint exceeded those in the longer, cranial half, implying that under stretch the input from Sps became higher toward the joint. In the non-extended muscle these lengths did not differ, although the lengths of extrafusal fibers isolated from 2 macerated muscles and normalized according to sarcomere length decreased linearily by approximately 50% along craniocaudal axis. It is explained that if elastic resistance of a Sp's sensory region exceeded that of an equivalent length of septal tissue in-series, the progressive shift in the ratio of compliances across this trapezoidally-shaped muscle should result in relatively greater lengthening of Sps at the shorter border as the muscle was extended. Levels of discharge conducive to transition of some motor units to the FOG type might be attained. Thus, gradients in the discharge of Sps (but not necessarily incidence) along both transverse and superficial-to-deep axes may be consistent with Sp sensory input influencing the distribution of at least these types of motor units.

Animals↗
PubMed2001

Longitudinal variation in muscle protein expression and contraction kinetics of largemouth bass axial muscle.

The present study investigates muscle protein expression in largemouth bass Micropterus salmoides through intra- and intermyomeric comparisons of white muscle. Using denaturing SDS-polyacrylamide gel electrophoresis, muscle protein expression in the arm and cone regions of sequential myomeres was compared for three bass. Low percentage (4.75 %) polyacrylamide-SDS gels and cyanogen bromide (CNBr) peptide mapping revealed no obvious intramyomeric differences between the myosin heavy chains of the arm and cone regions. Electrophoresis of myofibrils and muscle homogenates on higher percentage gels also failed to demonstrate any significant differences between arm and cone regions in either the myosin light chains or any of the major insoluble and soluble contractile proteins. Two differences were discovered intermyomerically: (i) the ratio of two troponin T isoforms changed from head to tail and (ii) caudal muscle had a lower total parvalbumin content than rostral muscle. Since troponin T and parvalbumin have been implicated in the regulation of skeletal muscle kinetics, longitudinal variation in muscle contraction kinetics was predicted. Subsequent experiments revealed that bass rostral white muscle showed faster rates of activation and relaxation than more caudal muscle, as has been observed in white muscle of other fish species. Rostral-caudal variations in white muscle protein composition and contractile properties are predicted to affect patterns of power production during fast, unsteady swimming.

Animals↗
PubMed1976

[Diameter changes of muscle fiber types of the inferior oblique muscle of the rabbit following denervation].

Changes in fibre diameters of extraocular muscles of the rabbit were studied at different times after denervation. The whole inferior oblique muscle hypertrophied, while some of the muscle fibres hypertrophied and others showed atrophy, depending on the fibre type. Fibre types have been determined by their histochemical enzyme profile. In the central layer of the muscle the phasic muscle fibres, which are rich in mitochondria, exhibited a transient hypertrophy being maximal 4-5 weeks after denervation and afterwards they atrophied; other phasic muscle fibres, which are poor in mitochondria, atrophied without having shown any sign of hypertrophy. Special, putatively slow tonic muscle fibres, which have low enzyme activities, underwent small long-lasting increases of their diameters. In the superficial layer of extraocular muscle there are two types of extremely thin muscle fibres rich in mitochondira. Both these fibre types hypertrophied to the greatest degree and for a very long time. Comparable changes in fibre diameters as described here for the muscle fibre types of an extraocular muscle are known from special muscle fibres in other vertebrate

Adenosine Triphosphatases↗
PubMed2004

Interrelationships among thigh muscle co-contraction, quadriceps muscle strength and the aerobic demand of walking in children with cerebral palsy.

The purpose of this study was to quantify interrelationships among thigh muscle co-contraction, quadriceps muscle strength, and the aerobic demand of walking in 13 children with spastic hemiplegic cerebral palsy (CP). During Session 1, subjects were familiarized with testing procedures, given five minutes of treadmill walking practice, and completed quadriceps muscle strength testing. In Session 2, subjects performed three 5-min walking bouts on the treadmill at 0.67 m x s(-1) to further accommodate to treadmill ambulation. During Session 3, resting VO2 was measured and subjects walked at 0.67, 0.89, and 1.12 m x s(-1) for five minutes while oxygen uptake (VO2) and thigh muscle co-contraction data were collected. Results demonstrated that no significant relationship existed between net VO2 and measures of thigh muscle co-contraction or quadriceps muscle strength. In addition, thigh muscle co-contraction was not shown to be associated with quadriceps muscle strength. Collectively, thigh muscle co-contraction and quadriceps muscle strength explained 13. 5%, 6.2%, and 2.2% of the variance in VO2 at 0.67, 0.89, and 1.12 m x s(-1), respectively. Viewed in concert, these results suggest that the walking energy expenditure of children with spastic hemiplegic CP is not influenced by the level of thigh muscle co-contraction or quadriceps muscle strength.

Cerebral Palsy↗