The number of satellite cells in slow and fast fibres from human vastus lateralis muscle

The aim of this investigation was to study the distribution of satellite cells in slow (type I fibres) and fast (type II fibres) fibres from human vastus lateralis muscle. This muscle is characterised by a mixed fibre type composition and is considered as the site of choice for biopsies in research work and for clinical diagnosis. Biopsy samples were obtained from five healthy young volunteers and a total of 1,747 type I fibres and 1,760 type II fibres were assessed. Satellite cells and fibre type composition were studied on serial muscle cross-sections stained with specific monoclonal antibodies. From a total of 218 satellite cells, 116 satellite cells were found in contact with type I fibres (53.6±8% of the satellite cells associated to type I fibres) and 102 satellite cells in contact with type II fibres (46.4±8% of the satellite cells associated to type II fibres). There was no significant difference (P=0.4) between the percentages of satellite cells in contact with type I and with type II fibres. Additionally, there was no relationship between the mean number of satellite cells per fibre and the mean cross-sectional area of muscle fibres. In conclusion, our results show that there is no fibre type-specific distribution of satellite cells in a human skeletal muscle with mixed fibre type composition.     

Effects of p.C430S polymorphism in the PPARGC1A gene on muscle fibre type composition and meat quality in Yorkshire pigs

The peroxisome proliferator‐activated receptor‐gamma coactivator‐1A (encoded by PPARGC1A) is involved in the formation of type I fibres. Therefore, the PPARGC1A gene can be considered as a functional candidate gene for muscle fibre type composition and meat quality in pigs. The aim of this study was to investigate the associations of the p.C430S polymorphic site in exon 8 of the PPARGC1A gene with muscle fibre characteristics and meat quality traits. The polymorphism was genotyped by PCR‐RFLP using AluI restriction enzyme on a total of 152 Yorkshire pigs. Statistical analyses revealed that the p.C430S genotypes significantly affected number (P < 0.05) and area (P < 0.01) of type I muscle fibre, and were significantly associated with muscle pH (P < 0.001) and lightness (P < 0.01). On the basis of these results, we suggest that the p.C430S polymorphism can induce variation of type I fibre formation in porcine longissimus dorsi muscle and that it can be used as a meaningful molecular marker for better meat quality.     

Do enzyme activities vary along muscle fibres?

Summary Distribution of succinate dehydrogenase activity along muscle fibres has been studied qualitatively by histochemistry on single microdissected rat muscle fibres and quantitatively by comparative kinetic microphotometry on longitudinal muscle sections. Qualitative staining reactions showed no appreciable variations in enzyme activity along the fibres regardless of fibre type. By quantitative assessment, minor variations were found along fibres but were within the range of the experimental error. These variations are of the same magnitudes as those observed in enzyme activities of pieces of the same fibre by means of quantitative microchemical methods performed in our laboratory (Spamer and Pette 1979; Nemeth et al. 1980a, b). Our results provide evidence that the enzyme levels are the same along the course of a muscle fibre.     

Fibre type regionalization of forelimb muscles in two mammalian species, Galea musteloides (Rodentia, Caviidae) and Tupaia belangeri (Scandentia, Tupaiidae), with comments on postnatal myogenesis

To investigate structural differences between propulsory and antigravity muscles, the spatial distribution of slow (type I) and fast (type II) muscle fibres in forelimb muscles of two species of small mammals was studied, Galea musteloides and Tupaia belangeri. Serial sections through complete forelimbs were prepared. Following histochemical fibre typing, the forelimbs were reconstructed three-dimensionally using product design software. Most forelimb muscles of both species showed a homogenous distribution of type I fibres. In the supraspinatus and triceps brachii (capita longum et laterale) muscles, however, a segregation of fibre types into ”fast” superficial areas and ”slow” deep regions was observed. Slow regions contained at least 60% type I fibres and were positioned along intramuscular extensions of the tendons of insertion. The functional implications of fibre type regionalization are discussed. An analysis of intramuscular fibre type distribution during postnatal myogenesis revealed no significant differences in muscle fibre differentiation between altricial and precocial juveniles. Differences in locomotor ability probably arise from heterochronic development of connective tissue components (endo- and perimysium). Accepted: 10 June 1999     

Training-induced alterations in muscle glycogen utilization in fibre-specific types during prolonged exercise

Using the glycogen depletion technique, we have examined utilization of specific fibre types during prolonged submaximal exercise to investigate the recruitment pattern employed by the central nervous system to sustain force generation in the face of a progressive glycogen depletion. Six male subjects (Vo2 max, 52.8 +/- 2.5 mL.kg-1.min-1, mean +/- SE) cycled at 59% of pretraining Vo2 max (the same absolute power output) for 99.5 +/- 6 min on two occasions, before training and after 10-12 days of intensive training, involving 2 h of cycling per day. Prior to the training, glycogen concentration during exercise in the type I and type IIA fibres of the vastus lateralis muscle as measured by microphotometric techniques was progressively reduced during exercise. The pattern of depletion in both of these fibre types was parallel and showed an early marked depletion amounting to 51 (p less than 0.05) and 35% (p less than 0.05) in the type I and type IIA fibres, respectively, during the first 15 min of exercise. At the end of exercise, glycogen levels in type I and type IIA fibres were reduced to 9 and 44% of initial levels, respectively. In contrast, glycogen concentration in type IIB fibres was not significantly (p less than 0.05) altered throughout the exercise. Following training, a pronounced glycogen sparing occurred that was conspicuous in only the type I and type IIA fibres, which was most pronounced during the first 15 min of the exercise. Similar to pretraining, glycogen concentrations in type IIB fibres were unaffected by either exercise or training.(ABSTRACT TRUNCATED AT 250 WORDS)     

The claw closer muscle of two estuarine crab species,Cyrtograpsus angulatus and Neohelice granulata (Grapsoidea,Varunidae): histochemical fibre type composition

Longo, M.V. and Díaz, A.O. (2011). The claw closer muscle of two estuarine crab species, Cyrtograpsus angulatus and Neohelice granulata (Grapsoidea, Varunidae): histochemical fibre type composition. —Acta Zoologica (Stockholm) 00 : 1–7. This study permitted the characterization of four types of muscle fibres in the claw closer muscles of Cyrtograpsus angulatus and Neohelice granulata. Succinic dehydrogenase (SDH) for mitochondria, periodic acid Schiff (PAS) for glycogen, Sudan Black B for lipids and myosin‐adenosine triphosphatase (m‐ATPase) preincubated at alkaline and acid pHs were used for that purpose. The mean fibre diameters, the relative areas and frequencies of each muscle fibre type were calculated. Types I and IV would be considered ‘extreme’ groups with type I fibres large, weak and acid/alkaline‐labile m‐ATPase, weak SDH, PAS and Sudan, and type IV fibres small, very strong and acid/alkaline‐resistant m‐ATPase, strong SDH and PAS, and moderate Sudan. Types II and III would belong to a predominant ‘intermediate’ group. Type IV fibres were scarce in C. angulatus but represented 25% of the total fibre population in N. granulata. In C. angulatus, the relative area occupied by type I fibres was bigger than its relative proportion, whereas in N. granulata, types I and II had similar patterns. Concluding, variations in fibre type composition in the claw closer muscles of C. angulatus and N. granulata would be linked to different habitats and feeding behaviours.     

Fibre types in locomotory muscles of the cartilaginous fish Chimaera monstrosa

The cartilaginous fish Chimaera monstrosa swims slowly by means of pectoral fin movements, and fast by undulations of the tail. In order to compare the fibres in the corresponding muscles, they were studied by histochemistry and electron microscopy. Three fibre types were identified by microphotometry and morphometry. Most of the axial muscles are white fibres, containing little mitochondria and glycogen. Red fibres, with glycogen and about 5 % mitochondria constitute a thin sheet in the axial muscles, composed of one fibre layer only. Pink fibres, with intermediate amounts of glycogen and mitochondria are situated between these two types, but are often not covered by red fibres. Pectoral muscles contain numerous red and intermediate fibres, partially mixed, superficially, and white fibres deeper. Pectoral muscle red fibres contain about 25 % mitochondria, half of which are situated in subsarcolemmal accummulations. The sarcotubular system has T-tubules at the Z discs, and the terminal cisternae are partially divided by regularly spaced clefts.     

Skeletal muscle characteristics of reindeer (Rangifer tarandus L.)

Fibre type composition, fibre areas, capillaries, enzyme activities and intramuscular substrates were analysed on skeletal muscle samples from reindeer. The muscles contained 10-20% Type I fibres and a higher percentage of Type IIB (40-60%) than Type IIA fibres (20-40%). All fibre types revealed medium or dark staining intensity for oxidative capacity. Glycolytic capacity was greatest in Type IIB fibres. All fibres stained for glycogen, while Type I and IIA fibres stained for lipids. The mean number of capillaries in contact with fibres of each type, relative to fibre type area was high in all muscle types. The metabolic profile of reindeer muscle indicates that energy, to a great extent, is produced through oxidative pathways.     

Immunohistochemical demonstration of fibre type-specific isozymes of cytochrome c oxidase in human skeletal muscle

Summary The immunohistochemical reaction of monoclonal as well as polyclonal antibodies against cytochrome c oxidase (COX) subunits with serial sections of normal human skeletal muscle was investigated. The stronger reactivity of polyclonal antibodies to COX subunits II–III and VIIbc with type I as compared to type II fibres, correlated well with the higher histochemical reactivity of NADH dehydrogenase, succinate dehydrogenase and cytochrome c oxidase in type I fibres. In contrast an almost exclusive reaction of a monoclonal antibody against subunit IV with type I fibre and a preponderan reaction of a polyclonal antibody against subunits Vab with type II fibres was obtained. Antibodies against subuntis I, Vb and VIc did not reveal a fibre-type-specific reactivity. The data indicate in human muscle the occurrence of fibre type-specific isozymes of cytochrome c oxidase differing in subunits IV and Va or Vb.     

Visualisation of capillaries in human skeletal muscle

 A double staining method combining Ulex europaeus agglutinin I lectin (UEA-I) and collagen type IV staining was used to determine the capillary density and the number of capillaries relative to different fibre types in human skeletal muscles. The result of this combined staining was compared with that of other staining methods including amylase-periodic acid Schiff (PAS), UEA-I, anti-collagen type IV and anti-von Willebrand factor. Muscle biopsy specimens, 12 from M. vastus lateralis and 6 from M. soleus, were obtained from 18 healthy young men. Compared with amylase-PAS staining, double staining showed a larger number of capillaries surrounding type I (+9.6%), type IIA (+8.6%) and type IIB (+11.6%) fibres in the M. vastus lateralis specimens (P<0.001 for all differences). The capillary to fibre ratio (cap·fibre^–1) and the capillary density (cap·mm^–2) were 8.3% (P<0.002) and 7.9% (P<0.001) larger, respectively. In the M. soleus specimens, cap·fibre^–1 and cap·mm^–2 were 7.4 and 9.9% larger, respectively, by double staining compared with PAS staining. Further comparisons showed that the cap·fibre^–1 and cap·mm^–2 obtained with double staining were similar to the values determined by the UEA-I staining, but greater than that measured by the collagen type IV method. The double staining gave a more marked stain of capillaries and revealed muscle fibre borders clearly, which is an advantage in studies that require comparisons between serial sections using computerised image analyses. It is concluded that the double staining method is superior to either the UEA-I, collagen type IV or the traditional amylase-PAS staining methods in analysing capillary density of normal human skeletal muscle. Accepted: 17 October 1996     

Congenital muscle fibre type disproportion: clinical, morphological and biochemical findings in children

Muscle biopsies from quadriceps femoris muscle of normal subjects and subjects with symptoms of congenital myopathy, aged 1-3 years, were examined for morphological and biochemical differences. Four patients showed clinical signs of Congenital Fibre Type Disproportion (CFTD) as described originally by Brooke (1973), while the other cases showed only signs of hypotonia and diffuse weakness as described by Clancy et al. (1980). No morphological differences between patients with different clinical signs were found in any biopsy sample from the quadriceps femoris muscle, as regards fibre size; type I fibres were always smaller than type II fibres. The difference in fibre size was more than 15% in all cases, and the variability coefficient of the larger type II fibres was less than 250. Nevertheless, as regards fibre occurrence, two patients showed more type I fibres than type II fibres, four patients showed more type II fibres than type I fibres and one patient had a marked type II fibre predominance. Enzyme activities assayed in the crude mitochondrial fraction showed no abnormalities between normal subjects and patients. An increase in the activity of lactate dehydrogenase in the crude extract was found in all cases.     

Differences in muscle sympathetic nerve response to isometric exercise in different muscle groups

The aim of this study was to examine the effects of muscle fibre composition on muscle sympathetic nerve activity (MSNA) in response to isometric exercise. The MSNA, recorded from the tibial nerve by a microneurographic technique during contraction and following arterial occlusion, was compared in three different muscle groups: the forearm (handgrip), anterior tibialis (foot dorsal contraction), and soleus muscles (foot plantar contraction) contracted separately at intensities of 20%, 33% and 50% of the maximal voluntary force. The increases in MSNA relative to control levels during contraction and occlusion were significant at all contracting forces for handgrip and at 33% and 50% of maximal for dorsal contraction, but there were no significant changes, except during exercise at 50%, for plantar contraction. The size of the MSNA response correlated with the contraction force in all muscle groups. Pooling data for all contraction forces, there were different MSNA responses among muscle groups in contraction forces (P = 0.0001, two-way analysis of variance), and occlusion periods (P = 0.0001). The MSNA increases were in the following order of magnitude: handgrip, dorsal, and plantar contractions. The order of the fibre type composition in these three muscles is from equal numbers of types I and II fibres in the forearm to increasing number of type I fibres in the leg muscles. The different MSNA responses to the contraction of different muscle groups observed may have been due in part to muscle metaboreflex intensity influenced by their metabolic capacity which is related to by their metabolic capacity which is related to the fibre type.     

Are region-specific changes in fibre types attributable to nonuniform muscle hypertrophy by overloading?

Muscle fibre composition was compared among the proximal (25%), middle (50%) and distal (75%) regions of the muscle length to investigate whether compensatory overload by removal of synergists induces region-specific changes of fibre types in rat soleus and plantaris muscles. In addition, we evaluated fibre cross-sectional area in each region to examine whether fibre recruitment pattern against functional overload is nonuniform in different regions. Increases in muscle mass and fibre area confirmed a significant hypertrophic response in the overloaded soleus and plantaris muscles. Overloading increased the percentage of type I fibres in both muscles and that of type IIA fibres in the plantaris muscle, with the greater changes being found in the middle and distal regions. The percentage of type I fibres in the proximal region was higher than that of the other regions in the control soleus muscle. In the control plantaris muscle, the percentage of type I and IIA fibres in the middle region were higher than that of the proximal and distal regions. With regard to fibre size, type IIB fibre area of the middle and distal regions in the plantaris increased by 51% and 57%, respectively, with the greater changes than that of the proximal region (37%) after overloading. These findings suggest that compensatory overload promoted transformation of type II fibres into type I fibres in rat soleus and plantaris muscles, with the greater changes being found in the middle and distal regions of the plantaris muscle.     

Immunohistochemical demonstration of fibre type-specific isozymes of cytochrome c oxidase in human skeletal muscle

The immunohistochemical reaction of monoclonal as well as polyclonal antibodies against cytochrome c oxidase (COX) subunits with serial sections of normal human skeletal muscle was investigated. The stronger reactivity of polyclonal antibodies to COX subunits II-III and VIIbc with type I as compared to type II fibres, correlated well with the higher histochemical reactivity of NADH dehydrogenase, succinate dehydrogenase and cytochrome c oxidase in type I fibres. In contrast an almost exclusive reaction of a monoclonal antibody against subunit IV with type I fibre and a preponderant reaction of a polyclonal antibody against subunits Vab with type II fibres was obtained. Antibodies against subunits I, Vb and VIc did not reveal a fibre-type-specific reactivity. The data indicate in human muscle the occurrence of fibre type-specific isozymes of cytochrome c oxidase differing in subunits IV and Va or Vb.     

Cellular patterns of post-mortem glycogenolysis in longissimus dorsi muscles of pigs at different live weights

Synopsis Serial frozen sections of longissimus dorsi muscles from twelve Canadian Yorkshire breed pigs at different live weights (13–86kg) were stained for glycogen by the periodic acid-Schiff (PAS) reaction and reacted for NAD tetrazolium reductase to determine the mitochondrial content of muscle fibres. Sections from muscles taken immediatelypost mortem and at 5 hrpost mortem were compared and the patterns of glycogenolysis in high, intermediate and low mitochondrial content fibres were assessed on the basis of the percentage of initially PAS-positive fibres which became PAS-negative 5 hrpost mortem. This form of assessment was necessary because not all fibres were PAS-positive immediatelypost mortem. In smaller pigs, only a few muscle fibres depleted their stainable glycogen by 5 hr and most of these fibres had a high mitochondrial content. In larger pigs, most or all initially PAS-positive fibres became PAS-negative by 5 hrpost mortem. Fibres with a low mitochondrial content accounted for most of the glycogenolysis detected histochemically in larger animals. The overall percentage of PAS-positive fibres was related to glycogen concentration (mg/g),r=0.52,P<0.025, when samples with all PAS-positive fibres were excluded.     

Metabolic capacity,fibre type area and capillarization of rat plantaris muscle. Effects of age,overload and training and relationship with fatigue resistance

• 1.1. The influences of age (5, 13 and 25-month-old rats), overload as obtained by denervation of synergists, and training on the metabolic capacity, relative muscle cross-sectional area occupied by each fibre type, capillarization and fatigue resistance of the rat m. plantaris were investigated.
• 2.2. Creatine kinase, phosphorylase and citrate synthase activities were lower in muscles of 25 than in those of 13-month-old rats (P < 0.001).
• 3.3. Overload resulted in an increased relative area of type I and II a fibres at all ages (P = 0.001).
• 4.4. Capillary density decreased with overload and increasing age (P < 0.001).
• 5.5. Fatigue resistance was higher in muscles of 13 than in those of 5-month-old rats (P < 0.05), and increased with overload (P < 0.05) at all ages.
• 6.6. Fatigue resistance of the whole muscle was not closely related to its oxidative capacity in contrast to what is generally found for single fibres or motor units.

     

NADH content in type I and type II human muscle fibres after dynamic exercise.

The effect of dynamic exercise on the NADH content of human type I (slow-twitch) and II (fast-twitch) muscle fibres was investigated. Muscle biopsy samples were obtained from the quadriceps femoris of seven healthy subjects at rest and after bicycle exercise at 40, 75 and 100% of the maximal oxygen uptake [VO2(max.)]. At rest and after exercise at 100% VO2(max.), muscle NADH content was significantly higher (P less than 0.05) in type I than in type II fibres. After exercise at 40% VO2(max.), muscle NADH decreased in type I fibres (P less than 0.01), but was not significantly changed in type II fibres. After exercise at 75 and 100% VO2(max.), muscle NADH increased above the value at rest in both type I and II fibres (P less than 0.05). Muscle lactate was unchanged at 40% VO2(max.), but increased 20- and 60-fold after exercise at 75 and 100% VO2(max.) respectively. The finding that NADH decreased only in type I fibres at 40% VO2(max.) supports the idea that type I is the fibre type predominantly recruited during low-intensity exercise. The increase of NADH in both fibre types after exercise at 75% and 100% VO2(max.) suggests that the availability of oxygen relative to the demand is decreased in both fibre types at high exercise intensities.     

The inheritance of skeletal muscle fibre composition in mice

Two inbred strains of mice C3H/HE and SWR, and generations produced by intercrossing, were studied to investigate the effect of heredity on muscle composition. The data were found to be consistent with a polygenic mode of inheritance. No simple effect of sex-linkage or maternal influence was evident. The heritability of fibre type percentage total fibre number and the relative size of Type I and Type II fibres were highly significant. Principal component analysis yielded a "genetic" vector which accounted for 57% of the variation in muscle fibre composition. Patterns of covariance of fibre type percentage, total fibre number and relative sizes of Type I and Type II fibres showed a single correlated response.     

New insights into skeletal muscle fibre types in the dog with particular focus towards hybrid myosin phenotypes

Electrophoresis, immunoblots, immunohistochemistry and image analysis methods were applied to characterise canine trunk and appendicular muscle fibres according to their myosin heavy chain (MyHC) composition and to determine, on a fibre-to-fibre basis, the correlation between contractile [MyHC (s), myofibrillar ATPase (mATPase) and sarco(endo)plasmic reticulum Ca²⁺-ATPase (SERCA) isoforms], metabolic [succinate dehydrogenase (SDH) and glycerol-3-phosphate dehydrogenase (GPDH) activities and glycogen and phospholamban (PLB) content] and morphological (cross-sectional area and capillary and nuclear densities) features of individual myofibres. An accurate delineation of MyHC-based fibre types was obtained with the developed immunohistochemical method, which showed high sensitivity and objectivity to delineate hybrid fibres with overwhelming dominance of one MyHC isoform. Phenotypic differences in contractile, metabolic and morphological properties seen between fibre types were related to MyHC content. All canine skeletal muscle fibre types had a relatively high histochemical SDH activity but significant differences existed in the order IIA>I>IIX. Mean GPDH was ranked according to fibre type such that I<IIA<IIX. Type IIA fibres were the smallest, type IIX fibres the largest and type I of intermediate size. Capillary and nuclear density decreased in the order IIA>I>IIX. Hybrid fibres, which represented nearly one third of the whole pool of skeletal muscle fibres analysed, had mean values intermediate between their respective pure phenotypes. Slow fibres expressed the slow SERCA isoform and PLB, whereas type II fibres expressed the fast SERCA isoform. Discrimination of myofibres according to their MyHC content was possible on the basis of their contractile, metabolic and morphological features. These intrafibre interrelationships suggest that myofibres of control dogs exhibit a high degree of co-ordination in their physiological, biochemical and morphological characteristics. This study demonstrates that canine skeletal muscle fibres have been misclassified in numerous previous studies and offers useful baseline data and new prospects for future work on muscle-fibre-typing in canine experimental studies.     

Changes in amino acid concentration in plasma and type I and type II fibres during resistance exercise and recovery in human subjects

Eight male subjects performed leg press exercise, 4 × 10 repetitions at 80% of their maximum. Venous blood samples were taken before, during exercise and repeatedly during 2 h of recovery. From four subjects, biopsies were taken from the vastus lateralis muscle prior to, immediately after and following one and 2 h of recovery. Samples were freeze-dried, individual muscle fibres were dissected out and identified as type I or type II. Resistance exercise led to pronounced reductions in the glutamate concentration in both type I (32%) and type II fibres (70%). Alanine concentration was elevated 60–75% in both fibre types and 29% in plasma. Glutamine concentration remained unchanged after exercise; although 2 h later the concentrations in both types of fibres were reduced 30–35%. Two hours after exercise, the plasma levels of glutamate and six of the essential amino acids, including the branched-chain amino acids were reduced 5–30%. The data suggest that glutamate acts as an important intermediate in muscle energy metabolism during resistance exercise, especially in type II fibres.