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 analysis of the human psoas major muscle with regards to the body side and aging

The aim of our study was to explore the age related changes of the fibre type composition of the human psoas major muscle. Moreover, we wanted to compare the fibre type composition of the left and right muscle. Muscle samples were collected from 15 young and 15 old males. Type I, IIA and IIX muscle fibres were typed using myosin heavy chain identification. The serial transverse sections were analysed using a light microscope. Results of our study showed that the age-related atrophy affected all three fibre types. Type IIA fibres were affected most profoundly while type I fibres were affected most weakly. The percentage of the different fibre types did not change during aging. There were no differences in the fibre type composition between the left and right muscle. Human psoas major muscle undergoes normal aging changes with the atrophy of all three fibre types, whereas atrophy most profoundly affects type IIA fibres. No differences in the fibre type composition between the left and right muscle point to the equal engagement of both legs in normal everyday activities of human.     

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.     

Alterations in human muscle fibre type distribution induced by acute exercise

Fibre type distributions in the vastus lateralis muscles of six male subjects (age 18 to 22 years) have been compared at rest and during exercise. Exercise consisted of one leg cycling at 60% VO2 max (one leg) for 120 min. The increased contractile activity was associated with a 28.8% (p less than 0.05) decrease in the distribution of Type I fibres in the exercised leg. This change in fibre type distribution was manifested early in the exercise (15 min), and was also evident in muscle samples obtained after 60 and 120 min of activity. Reductions in the Type I fibre distribution was accompanied by an increase in the Type II fibres, specifically the Type IIA distribution (p less than 0.05). Comparable alterations in the specific fibre distribution were also found in the non exercising leg. These observations indicate that alterations in the muscle cell induced either directly or indirectly by the increased contractile activity interact with normal pre-incubation conditions to effect changes in the stability of the myofibrillar ATPase reaction. Specifically, it appears that a percentage of the Type I fibre population becomes acid labile and alkali stable.     

Relationship between myosin heavy chain IId isoform and fibre types in soleus muscle of the rat after hindlimb suspension

The relationship between the myosin heavy chain (HC) IId isoform and histochemically defined fibre types was investigated in the rat soleus muscle after hindlimb suspension. After 4 weeks of suspension, right and left muscles were removed and fibre type composition and total fibre number were examined by histochemical myosin adenosine triphosphatase staining sections. Myosin HC isoforms were analysed by sodium dodecyl sulphate polyacrylamide gel electrophoresis. After the suspension, there was a significant decrease in the percentage of type I fibres and a concomitant increase in that of type IIa fibres. However, the total number of fibres was not affected by suspension. The synthesis of HC IId isoform, which was not found in the control, and the decrease in the ratio of slow type myosin heavy chain isoform (HC I) were observed after suspension. These results would may suggest that the change of fibre type composition was caused by a shift from type I to IIa fibres after suspension. Furthermore, it could be suggested that the synthesis of HC IId isoform occurred during the stage of type shift from type I to IIa fibres.     

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.     

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.     

Histology of skeletal muscle in adults with GH deficiency: comparison with normal muscle and response to GH treatment.

The histology of needle biopsy specimens of skeletal muscle from the vastus lateralis was quantitatively assessed in a group of adults with growth hormone (GH) deficiency, most of whom had hypopituitarism treated with conventional pituitary hormone replacement. The mean age of the 21 patients (16 males and 5 females) was 39 +/- 2 (SEM). Comparisons were made with age- and sex-matched controls following six months double-blind, placebo-controlled treatment with recombinant human GH (rhGH) in the GH-deficient patients. Before treatment, needle muscle biopsies from patients with GH deficiency showed mean type I and II fibre areas of 5,153 +/- 273 and 4,828 +/- 312 microns 2 respectively, which did not differ from the controls (4,482 +/- 306 and 4,699 +/- 310 microns 2). Percentages of type I fibres were similar in the two groups (47.2 +/- 2.5% in GH deficiency and 45.3 +/- 2.2% in controls). No difference in the variability of type I or II fibre areas was demonstrated between the groups. Correlations between the relative contribution to total fibre area by type I fibres (mean fibre area x percent) and maximal oxygen uptake (p = 0.006), and between type II fibres and quadriceps force (p = 0.035) were noted in GH-deficient adults before treatment. Following rhGH treatment, no change was noted in mean fibre areas, variability of fibre areas, or percentage of either fibre type.(ABSTRACT TRUNCATED AT 250 WORDS)     

Factors affecting the histochemical composition of reinnervated soleus muscle of rat.

The myofibrillar ATPase reaction was utilized to determine the relative proportion of type II fibres in reinnervated soleus muscle 6 months after transection and reunion of the nerve at various distances from the muscle. In self-reinnervated soleus muscle, a highly significant decrease in the percentage of type II fibres from 10.5 +/- 1.6% in normal muscle to 0.7 +/- 0.4% was noted. In randomly reinnervated soleus muscle the percentage of type II fibres gradually increased with the distance of the site of nerve transection from the muscle. After transection and reunion of the muscular branch of the tibial nerve, the type II fibres constituted 34.0 +/- 1.5% and that of the reinnervated soleus muscle after transection and reunion of the sciatic nerve stump was 73.7 +/- 1.7% of the total fibre population. Different factors which might be responsible for the observed differences in the degree of cytochemical transformation of muscle fibre types in the process of reinnervation are discussed.     

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.     

Extreme endurance training: evidence of capillary and mitochondria compartmentalization in human skeletal muscle.

Biopsies from the medial gastrocnemius muscle of three experienced endurance runners who had completed an ultramarathon run (160 km) the previous day were assessed for their oxidative characteristics (fibre types, capillarization and mitochondria content). Also, a regional comparison was made for fibres located centrally (completely surrounded by other fibres) versus fibres located peripherally (next to the interfascicular space) and the capillarization of these peripheral fibres was determined. Subsarcolemmal mitochondria were abundant and 'compartmentalized' close to the capillaries. The number of capillaries around fibres ranged from 5.8 to 8.5 and 5.7 to 8.5, and the number of capillaries.mm-2 ranged from 665 to 810 and 727 to 762, for type I (slow twitch) and type II (fast twitch) fibres, respectively. Central fibres contained a greater number of capillaries and more capillaries.mm-2 than their peripheral counterparts. Peripheral fibres contained more capillaries.micron-1 between fibres than at the interfascicular space. Type I fibres were more distributed (63%-78%) and larger than type II fibres. An abundance of subsarcolemmal mitochondria located close to the capillaries, efficient capillary proliferation between fibres where sharing can occur and greater relative distribution and size of type I fibres are, collectively, efficient characteristics of extreme endurance training.     

The relationship of voluntary running to fibre type composition, fibre area and capillary supply in rat soleus and plantaris muscles

Twenty 4-week-old Wistar rats exercised voluntarily in running wheels each day for 45 days. Fibre type composition, fibre cross-sectional area and the number of capillaries around a fibre of the slow-twitch soleus and fast-twitch plantaris muscles were examined and compared with animals which had no access to running wheels. The exercise group had a higher percentage of fast-twitch oxidative glycolytic (FOG) fibres and a lower percentage of fast-twitch glycolytic (FG) fibres in the deep portion of the plantaris muscle. The area of FOG fibres in the surface portion of the plantaris muscle was also greater in the exercise group. In the exercised animals, there was a positive relationship between the running distance and the area of FOG fibres in both the deep and surface portions of the plantaris muscle. In addition, the running distance correlated positively with the percentage of FOG fibres and negatively with that of FG fibres in the deep portion of the plantaris muscle. There were no relationships between the running distance and fibre type composition, or fibre area and capillary supply in the soleus muscle. These results suggested that the increase in the percentage and area of FOG fibres in the fast-twitch muscle was closely related to voluntary running.     

Morphological,histochemical and stereological analysis of the female canine M. urethralis

The M. urethralis was morphologically investigated in ten medium-sized female dogs of different breeds and age, as well as histochemically and stereologically analysed in a homogeneous group of five female beagles. Macroscopically, the muscle was essentially confined to the distal third and most strongly developed in the fourth quarter of the urethra. Here, it surrounded the urethra transversely at the ventral and lateral aspects, passing with its caudal fibres dorsally onto the vagina. The muscle fibres were assembled in groups of different sizes and usually separated by thick connective tissue septae. Based on the myofibrillar actomyosin ATPase (mATPase) reaction, type I and two main subtype II fibres could be differentiated. Type II fibres were, however, indistinguishable by their metabolic enzyme activities since both subclasses displayed oxidative-glycolytic properties. The subtype II fibres containing the more acidlabile mATPase activity were classified as IIA, whereas the other main subtype was designated IIS (subtype) and considered as peculiar to the dog. In addition, the investigation revealed a rare fibre type exhibiting the histochemical profile of IIC fibres. There was no evidence of classical glycolytic IIB fibres. The M. urethralis was composed of 24% type I and 76% type II fibres with an average diameter of 34.9 and 28.5 m, respectively. Connective tissue constituted 52.8% of the total muscle volume. Due to the predominance of fast twitch II fibres, the urethral muscle is not designed to maintain a high tone over long periods of time. Its primary role is to function rapidly and intermittently guaranteeing urinary continence during stress situations when other continence factors are overburdened.     

Effects of training on fibre composition in rat gastrocnemius muscle

Forty-eight adult Wistar rats were divided into four groups for experimentation. The group I was used as a control and groups II, III and IV underwent progressive treadmill training. Samples of the red and mixed portions of m. gastrocnemius (lateral head) were stained with the histochemical technique of m-ATPase to determine the percentage of type I, IIA and IIB fibres, and with NADH-TR, in order to quantify variations in "low-oxidative" fibre percentages. The results showed that progressive training did not lead to statistical variations in the percentage of type I fibres. However, the proportion of type IIA fibres rose, while that of IIB fibres fell, in both cases significantly. Variations were more marked in mixed than in red Gastrocnemius muscle. A clear decrease was noted in "low-oxidative" fibres, which were virtually absent from red portion. This decrease was more marked, and occurred more rapidly, than in type IIB fibres.     

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 fibre type composition of the striated muscle of the oesophagus in ruminants and carnivores

Summary The fibre type composition of the striated muscle layer of the oesophagus of the cow, sheep, donkey, dog and cat was examined with standard histochemical methods and immunohistochemical staining using type-specific antimyosin sera. The heavy chain and light chain composition of oesophageal myosin was also examined using electrophoretic peptide mapping and 2-dimensional gel electrophoresis respectively. In the ruminants and donkey the oesophagus was composed of fibre types I, IIA and IIC with immunohistochemical characteristics identical to those of the same fibre types found in control skeletal muscle. In the ruminants there was a gradient in the proportion of type I fibres from 1% (at the cervical end) to about 30% (at the caudal end).In the carnivores the oesophageal muscle was composed of a very small percentage of type I and IIC fibres, but the predominant type was very different hisotchemically and immunohistochemically from all the fibre types (I, IIA, IIB, IIC) present in the control muscles. This oesophageal fibre type (IIoes) had an acid- and alkaline-stable m-ATP-ase activity, a moderate histochemical Ca-Mg actomyosin ATPase activity, and reacted weakly with anti-IIA and antiIIB myosin sera. Although the light chains of the IIoes myosin were the same as the light chains of a mixture of IIA and IIB myosins, their respective heavy chains gave different peptide maps. Greater differences were obtained between the heavy chains of IIoes and other striated muscle myosins.These observations lead us to conclude that this predominant fibre type of the carnivore oesophageal striated muscle is of the fast type, and contains a distinct isoform of myosin similr but not identical to the other fast type myosins.     

Lactate dehydrogenase isozymes in type I,IIA and IIB fibres of rabbit skeletal muscles

Summary Lactate dehydrogenase (LDH) isozyme patterns were analysed by polyacrylamide (PAA) slab gel electrophoresis in extracts prepared from various rabbit skeletal muscles of defined fibre composition and by PAA microelectrophoresis of microdissected, histochemically typed single muscle fibres. The results obtained by electrophoresis of whole muscle extracts generally agreed with the data obtained from single fibre electrophoresis, i.e. the LDH isozyme pattern corresponded to that of the predominant fibre type. Type I Fibres from soleus and semitendinosus muscles were characterized by a unique pattern of all 5 LDH isozymes with a predominance of LDH-1, 2 and 3. The major fraction (80%) of the type II fibres from extensor digitorum longus and tibialis anterior muscles contained only LDH-5 (M₄). About 20% of the type II fibres contained in addition to LDH-5 small amounts of LDH-4 and LDH-3. The fraction of fibres containing LDH-5, LDH-4, and LDH-3 was similar (ca. 20%) in the histochemically defined IIA and IIB subpopulations In view of the fact that the major fractions of rabbit IIB fibres display low and of IIA fibres high aerobic oxidative capacities (Reichmann and Pette 1982), these data indicate that the expression of the H-subunit of LDH is not correlated with the aerobic-oxidative capacity of the fibre. It also appears not to be correlated with the presence of different myosin isoforms in IIA and IIB fibres.     

Histoenzymatic characterization of sub-types of type I fibres in fast muscles of rats.

The histochemical activities of succinic dehydrogenase (SDH), myofibrillar Adenosine triphosphatase (ATPase) and alpha glycerophosphate dehydrogenase were studied in serial sections of rat vastus lateralis (red) (RVL), gastrocnemius and diaphragm muscles. Three main fibre-types were distinguished. The "Type I" fibres of RVL and gastrocnemius muscles fell into two distinct groups: one category--"Type IA" showed very low ATPase activity. The second category of "Type IB" fibres displayed moderate ATPase reaction. The "Type IA" fibres were divisible into two sub-groups when tested for SDH reaction. "Type IA1" fibres possessed a homogenous distribution of diformazan granules throughout the fibre: "Type IA2" fibres displayed characteristic "moth-eaten" pattern of diformazan localization. The diaphragm muscle did not show either "Type IB" or "Type IA2" varieties. The great majority of TypeI fibres were sub-type IA1 in the three fast muscles studied. It is also demonstrated here that an inherent heterogeneity exists between Type I filores of diaphragm and leg muscles in regard to alpha-GPD localization. This histochemical data emphasizes the fact that subdivision of TypeI striated muscle fibres of mammalian animals into two sub-types is only approximate and that a further subcategorization is possible.     

Variations in fibre composition of the gastrocnemius muscle in rats subjected to speed training

Thirty-six adult Wistar rats were divided into three groups. One group was used as a control, and the other two underwent different training programmes in which greater relevance was attached to the intensity of exercise than to its duration. Samples of the red and mixed portions of m. gastrocnemius (caput lateralis) were stained with m-ATPase to determine the percentage of type I, IIA and IIB fibres, and with NADH-TR in order to quantify variations in the percentage of low staining intensity (FG) fibres. The most notable results obtained were: a) the ratio of type I type II fibres remained unchanged; b) the proportion of IIA fibres increased, while that of IIB fibres decreased correspondingly; c) FG fibres, which were virtually absent from the red portion, recorded a clear decrease which was more marked, and occurred more rapidly, than in IIB fibres. These differences were all statistically significant in the mixed portion of the muscle. Adaptive changes in fibre composition in the red portion were less marked.     

Fibre-type specificity and effect of thyroid hormone on glucose 6-phosphate dehydrogenase activity in normal and denervated skeletal muscles of the rat

Summary Glucose-6-phosphate dehydrogenase activity increases following denervation of rat skeletal muscle. The specificity of this effect to muscle fibre type was studied. Basal activity of the dehydrogenase was higher in soleus, a muscle composed predominantly of type I fibres, than in extensor digitorum longus, a muscle composed predominantly of type IIa and b fibres. The enzymatic activity of the soleus was also greater than that of the red (RQ) and white (WQ) portions of quadriceps muscle (predominantly type IIa and type IIb fibres, respectively). Following denervation, glucose-6-phosphate dehydrogenase increased in extensor digitorum longus and RQ, but not in WQ or the soleus. Following chronic treatment of rats with 3,3,5-triiodothyronine, which converts type I muscle fibres to type II, the dehydrogenase activity increased in both denervated soleus and extensor digitorum longus. It is concluded that the effect of denervation on glucose-6-phosphate dehydrogenase activity is selective for type IIa (fast oxidative-glycolytic) muscle fibres.