Fiber number, area, and composition of mouse soleus muscle following enlargement

Muscle fiber number, cross-sectional area, and composition were studied in response to enlargement produced by synergistic ablation in the mouse soleus muscle. The effect of the location of a histological section on the number of fibers that appear in the section was also studied using the mouse soleus muscle. Enlargement was produced in the soleus muscle of 15 male and 15 female mice by ablation of the ipsilateral gastrocnemius muscle. Fiber counts, using the nitric acid digestion method, revealed no difference between control and enlarged muscles in male and female mice. Mean fiber area, determined by planimetry, was 49.1 and 34.5% greater following enlargement in male and female mice, respectively. Increase in muscle weight could be totally accounted for by the increase in fiber area following enlargement. A transformation of type II to type I fibers occurred following enlargement for both sexes. Counts of fibers from histological sections revealed that there was a progressive decrease in the fiber number as the section was moved from the belly to the distal end of the muscle. The results of these studies indicate that muscle enlargement in the mouse soleus muscle is due to hypertrophy of the existing muscle fibers.     

Histochemical and electronmicroscopical analysis of muscle fiber in myotomes of teleost fish (Noemacheilus barbatulus L.)

A quantitative histochemical study was carried out on axial musculature of Noemacheilus barbatulus L. On the basis of succinate dehydrogenase (SDH) and myofibrillar ATP-ase activity, 5 types of muscle fibers are described. When the SDH method was used, red, tonic, intermediate, and white muscle fibers were easily observed. However, histochemical reaction for myofibrillar ATP-ase activity, after alkaline preincubation (pH = 10.4), revealed another type of fiber zone laying between the intermediate and white muscle fiber regions and forming a transitional zone. Electron microscopic observation showed significant differences in sarcomere organization and thickness of myosin filaments of the various muscle fiber types.     

Histochemical patterns in normal and splaylegged piglet muscle fibers

Summary The histochemical pattern of muscle fiber types of the longissimus dorsi and biceps femoris muscles was investigated in normal and splaylegged piglets at birth and seven days later. Only slight differences between the muscle fibers at birth were found using histochemical reactions for alkaline adenosine triphosphatase (ATPase), succinate dehydrogenase (SDH), phosphorylase (PH) activities, and for the periodic acid-Schiff (PAS) reaction. With the method for acid-preincubated ATPase activity, high activity was observed in Type I muscle fibers and low activity in Type II muscle fibers in animals of both groups investigated. However, a higher number of Type I fibers was found in muscles of normal piglets, suggesting a faster and more advanced process of transformation of Type II into Type I muscle fibers in unaffected animals. Thus the histochemical conversion appears to be retarded in muscles of splaylegged animals, which have a histochemical pattern similar to that of normal prenatal animals. Cholinesterase activity in motor endplates was well developed; its staining revealed smaller sized and irregularly arranged endplates in muscles of affected piglets. Fiber type differentiation in muscles of animals which recovered from splayleg becomes fully developed and comparable to normal piglets seven days after birth. The number of fibers which became converted from Type II to Type I was increased; the fiber types were differentiated with regard to the PAS reaction and to their ATPase, SDH and PH activities. Morphological features of motor endplates in muscles of normal and surviving splaylegged piglets are similar.Histochemical investigation of the fiber type differentiation thus suggests that full recovery occurs within the first week of postnatal life in muscles affected by pathological changes accompanying splayleg.     

Histochemical patterns in normal and splaylegged piglet muscle fibers

The histochemical pattern of muscle fiber types of the longissimus dorsi and biceps femoris muscles was investigated in normal and splaylegged piglets at birth and seven days later. Only slight differences between the muscle fibers at birth were found using histochemical reactions for alkaline adenosine triphosphatase (ATPase), succinate dehydrogenase (SDH), phosphorylase (PH) activities, and for the periodic acid-Schiff (PAS) reaction. With the method for acid-preincubated ATPase activity, high activity was observed in Type I muscle fibers and low activity in Type II muscle fibers in animals of both groups investigated. However, a higher number of Type I fibers was found in muscles of normal piglets, suggesting a faster and more advanced process of transformation of Type II into Type I muscle fibers in unaffected animals. Thus the histochemical conversion appears to be retarded in muscles of splaylegged animals, which have a histochemical pattern similar to that of normal prenatal animals. Cholinesterase activity in motor endplates was well developed; its staining revealed smaller sized and irregularly arranged endplates in muscles of affected piglets. Fiber type differentiation in muscles of animals which recovered from splayleg becomes fully developed and comparable to normal piglets seven days after birth. The number of fibers which became converted from Type II to Type I was increased; the fiber types were differentiated with regard to the PAS reaction and to their ATPase, SDH and PH activities. Morphological features of motor endplates in muscles of normal and surviving splaylegged piglets are similar. Histochemical investigation of the fiber type differentiation thus suggests that full recovery occurs within the first week of postnatal life in muscles affected by pathological changes accompanying splayleg.     

Composition of muscle fibers in the slow loris,using the m. biceps brachii as an example

Histological examination of the skeletal muscle of the slow loris, which displays slow movement and locomotion among the prosimians, revealed a muscle fiber composition which differed from the general condition in mammals. Three types of muscle fiber cells were therefore analyzed quantitatively in order to elucidate their specificity. The skeletal muscle of the limbs of the slow loris was predominantly composed of red muscle fibers (type I) showing persistent tonic contraction.     

Resistance training induces qualitative changes in muscle morphology, muscle architecture, and muscle function in elderly postoperative patients.

Although the negative effects of bed rest on muscle strength and muscle mass are well established, it still remains a challenge to identify effective methods to restore physical capacity of elderly patients recovering from hospitalization. The present study compared different training regimes with respect to muscle strength, muscle fiber size, muscle architecture, and stair walking power in elderly postoperative patients. Thirty-six patients (60-86 yr) scheduled for unilateral hip replacement surgery due to hip osteoarthritis were randomized to either 1) resistance training (RT: 3/wk x 12 wk), 2) electrical stimulation (ES: 1 h/day x 12 wk), or 3) standard rehabilitation (SR: 1 h/day x 12 wk). All measurements were performed at baseline, at 5 wk and 12 wk postsurgery. After 12 wk of resistance training, maximal dynamic muscle strength increased by 30% at 60 degrees /s (P < 0.05) and by 29% at 180 degrees /s (P < 0.05); muscle fiber area increased for type I (+17%, P < 0.05), type IIa (+37%, P < 0.05), and type IIx muscle fibers (+51%, P < 0.05); and muscle fiber pennation angle increased by 22% and muscle thickness increased by 15% (P < 0.05). Furthermore, stair walking power increased by 35% (P < 0.05) and was related to the increase in type II fiber area (r = 0.729, P < 0.05). In contrast, there was no increase in any measurement outcomes with electrical stimulation and standard rehabilitation. The present study is the first to demonstrate the effectiveness of resistance training to induce beneficial qualitative changes in muscle fiber morphology and muscle architecture in elderly postoperative patients. In contrast, rehabilitation regimes based on functional exercises and neuromuscular electrical stimulation had no effect. The present data emphasize the importance of resistance training in future rehabilitation programs for elderly individuals.     

Sarcocystis found in the skeletal muscle of common squirrel monkeys

Abnormally enlarged muscle fiber cells of ring form were incidentally detected in transverse sections of muscles of the common squirrel monkey during microscopic investigation of the composition of muscle fibers. Longitudinal sections showed slender capsule-like cysts in the sarcoplasm. Detailed examination revealed these cysts to be those ofSarcocystis. Among the three types of muscle fiber cells that compose the skeletal muscle, staining with Sudan black B revealed that this parasite selectively infested type II white fibers with a large diameter and a high glycogen content.     

Histochemical, biochemical, and ultrastructural analyses of single human muscle fibers, with special reference to the C-fiber population.

A muscle biopsy from the vastus lateralis muscle of a strength-trained woman was found to contain an unusual fiber type composition and was analyzed by histochemical, biochemical, and ultrastructural techniques. Special attention was given to the C-fibers, which comprised over 15% of the total fiber number in the biopsy. The mATPase activity of the C-fibers remained stable to varying degrees over the pH range normally used for routine mATPase histochemistry. Although a continuum existed, the C-fibers were histochemically subdivided into three main fiber types: IC, IIC, and IIAC. The IC fibers were histochemically more similar to the Type I, the IIAC were more similar to the Type IIA, and the IIC were darkly stained throughout the pH range. Biochemical analysis revealed that all C-fibers coexpressed myosin heavy chains (MHC) I and IIa in variable ratios. The histochemical staining intensity correlated with the myosin heavy chain composition such that the Type IC fibers contained a greater ratio of MHCI/MHCIIa, the IIAC contained a greater ratio of MHCIIa/MHCI, and the Type IIC contained equal amounts of these two heavy chains. Ultrastructural data of the C-fiber population revealed an oxidative capacity between fiber Types I and IIA and suggested a range of mitochondrial volume percent from highest to lowest such that I greater than IC greater than IIC greater than IIA-C greater than IIA. Under physiological conditions, it appears that the IC fibers represent Type I fibers that additionally express some fast characteristics, whereas the Type IIAC are Type IIA fibers that additionally express some slow characteristics. Fibers expressing a 50:50 mixture of MHCI and MHCIIa (IIC fibers) were rarely found. It is not known whether C-fibers represent a distinct population between the fast- and slow-twitch fibers that is specifically adapted to a particular usage or whether they are transforming fibers in the process of going from fast to slow or slow to fast.     

Mutation of the IIB myosin heavy chain gene results in muscle fiber loss and compensatory hypertrophy

The fast skeletal IIb gene is the source of most myosin heavy chain (MyHC) in adult mouse skeletal muscle. We have examined the effects of a null mutation in the IIb MyHC gene on the growth and morphology of mouse skeletal muscle. Loss in muscle mass of several head and hindlimb muscles correlated with amounts of IIb MyHC expressed in that muscle in wild types. Decreased mass was accompanied by decreases in mean fiber number, and immunological and ultrastructural studies revealed fiber pathology. However, mean cross-sectional area was increased in all fiber types, suggesting compensatory hypertrophy. Loss of muscle and body mass was not attributable to impaired chewing, and decreased food intake as a softer diet did not prevent the decrease in body mass. Thus loss of the major MyHC isoform produces fiber loss and fiber pathology reminiscent of muscle disease.     

A histochemical and enzymatic study of the muscle fiber types in the water monitor, Varanus salvator

Histochemical analysis of five muscles from the water monitor, Varanus salvator, identified three major classes of fibers based on histochemical activities of the enzymes myosin ATPase (mATPase), succinic dehydrogenase (SDH), and alpha-glycerophosphate dehydrogenase (alpha GPDH). Fast-twitch, glycolytic (FG) fibers were the most abundant fiber type and exhibited the following reaction product intensities: mATPase, dark; SDH, light; alpha GPDH, moderate to dark. Fast-twitch, oxidative, glycolytic (FOG) fibers were characteristically mATPase, dark; SDH, light; alpha GPDH, moderate to dark. The third class of fibers had the following histochemical characteristics: mATPase, light; SDH, moderate to dark; alpha GPDH, light. These fibers were considered to be either slow twitch, or tonic, and oxidative (S/O). Pyruvate kinase (PK), alpha GPDH, and citrate synthase (CS) activities were measured in homogenates of the same muscles studied histochemically. There was a positive relationship between both PK and alpha GPDH activities and the percentage of glycolytic fiber types within a muscle. Likewise, CS activities were greater in muscles high in FOG and S/O content. Based on CS activities, Varanus S/O fibers were eight-fold more oxidative than FG fibers within the same muscle. PK/CS ratios suggested that FG fibers possess high anaerobic capacity, similar to the iguanid lizard Dipsosaurus. The fiber type composition of the gastrocnemius muscle, relative to that of other lizard species, suggests that varanid lizards may possess a greater proportion of FOG and S/O fibers than other lizards.     

Light and electron microscopic serial analysis of mouse extraocular muscle: Morphology,innervation and topographical organization of component fiber populations

Mouse superior rectus extraocular muscle was examined in serial section by light and electron microscopy. By such analysis, it was possible to discriminate single versus multiple innervation, characteristics of internal cell morphology, and topographical distribution of the respective fiber populations within the muscle. Singly innervated (SIF) and multiply innervated fibers (MIF) were observed, both in an orbital surface layer and in the underlying global region of the muscle. Five morphologically distinct fiber types (three SIF and two MIF) were discriminable in terms of fiber diameter, mitochondrial richness, development of the sarcoplasmic reticulum, and myofibrillar size. Many fibers, both SIF and MIF, terminated variously along the length of the muscle. The diameter of orbital MIF typically varied from one end of the fiber to the other by a factor of about three; the global MIF were of essentially constant diameter. The junctional complexity varied among the respective types of SIF. The MIF of both the global and orbital regions exhibited comparable ranges of complexity in their neuromuscular junctions.     

A comparison of muscle fiber characteristics at different levels of the vertebral column in the rhesus monkey

The vertebral muscle fiber characteristics of adult female rhesus monkeys have been examined. Muscle samples were obtained from precisely defined superficial and deep sites on both sides of the vertebral column. In particular, samples were collected from three different levels of the column and the muscle fiber characteristics from all these different sites were compared. It is clear that in the rhesus monkey at least, muscle fiber characteristics are dependent on the vertebral level although not necessarily on the side of the vertebral column.     

Skeletal muscle adaptations to microgravity exposure in the mouse.

To investigate the effects of microgravity on murine skeletal muscle fiber size, muscle contractile protein, and enzymatic activity, female C57BL/6J mice, aged 64 days, were divided into animal enclosure module (AEM) ground control and spaceflight (SF) treatment groups. SF animals were flown on the space shuttle Endeavour (STS-108/UF-1) and subjected to approximately 11 days and 19 h of microgravity. Immunohistochemical analysis of muscle fiber cross-sectional area revealed that, in each of the muscles analyzed, mean muscle fiber cross-sectional area was significantly reduced (P < 0.0001) for all fiber types for SF vs. AEM control. In the soleus, immunohistochemical analysis of myosin heavy chain (MHC) isoform expression revealed a significant increase in the percentage of muscle fibers expressing MHC IIx and MHC IIb (P < 0.05). For the gastrocnemius and plantaris, no significant changes in MHC isoform expression were observed. For the muscles analyzed, no alterations in MHC I or MHC IIa protein expression were observed. Enzymatic analysis of the gastrocnemius revealed a significant decrease in citrate synthase activity in SF vs. AEM control.     

An analysis of the factor structure of the histochemical phenotype of normal muscle fiber and muscle fiber during a change in the functional load

Using dispersive and factor analyses of the serial sections of the skeletal muscle tissue it has been shown that the activity of myosin Ca-ATPase is the most essential parameter in the definition of the phenotype of skeletal muscle fiber according to its functional and metabolic characteristics. The stability of this parameter during different functional loadings permits to recommend it as the major one in the definition of the fiber phenotype.     

Biochemical and histochemical studies on skeletal muscle in rat during the course of development. The biochemical properties of type 2C muscle fiber

1. Biochemical and histochemical analyses were performed on skeletal rat muscles over the course of development from neonate to adult. 2. A small amount of triglyceride and a large amount of glycogen were found to be contained in neonatal type 2C muscle fiber; based on this finding the main energy metabolism in this fiber was thought to be anaerobic glycolysis. 3. Moreover at 10 days type 2C muscle fiber was shown to contain a large amount of triglyceride. 4. These results suggest that, although histochemical characteristics remain the same, biochemical properties change during the course of muscle development.     

Adiponectin is expressed by skeletal muscle fibers and influences muscle phenotype and function

Adiponectin (Ad) is linked to various disease states and mediates antidiabetic and anti-inflammatory effects. While it was originally thought that Ad expression was limited to adipocytes, we demonstrate here that Ad is expressed in mouse skeletal muscles and within differentiated L6 myotubes, as assessed by RT-PCR, Western blot, and immunohistochemical analyses. Serial muscle sections stained for fiber type, lipid content, and Ad revealed that muscle fibers with elevated intramyocellular Ad expression were consistently type IIA and IID fibers with detectably higher intramyocellular lipid (IMCL) content. To determine the effect of Ad on muscle phenotype and function, we used an Ad-null [knockout (KO)] mouse model. Body mass increased significantly in 24-wk-old KO mice [+5.5 +/- 3% relative to wild-type mice (WT)], with no change in muscle mass observed. IMCL content was significantly increased (+75.1 +/- 25%), whereas epididymal fat mass, although elevated, was not different in the KO mice compared with WT (+35.1 +/- 23%; P = 0.16). Fiber-type composition was unaltered, although type IIB fiber area was increased in KO mice (+25.5 +/- 6%). In situ muscle stimulation revealed lower peak tetanic forces in KO mice relative to WT (-47.5 +/- 6%), with no change in low-frequency fatigue rates. These data demonstrate that the absence of Ad expression causes contractile dysfunction and phenotypical changes in skeletal muscle. Furthermore, we demonstrate that Ad is expressed in skeletal muscle and that its intramyocellular localization is associated with elevated IMCL, particularly in type IIA/D fibers.     

Muscle fiber characteristics of pectoralis major muscle as related to muscle mass in different Japanese quail lines

The objectives of this study were to investigate the muscle fiber characteristics of the pectoralis major muscle, and its relation to growth performance in the random bred control (RBC) and heavy weight (HW) Japanese quail lines at 42 days of age. The HW line had greater body (232.0 v. 100.2 g, P < 0.001) and pectoralis major muscle (19.0 v. 6.2 g, P < 0.001) weights than the RBC line. Color differences were observed between the superficial and deep regions of the pectoralis major muscle, with the superficial region showing a higher value of lightness than the deep region of the RBC or HW lines (P < 0.001). The percentage of the superficial region in the pectoralis major muscle was higher in the HW line compared with the RBC line (46.2% v. 38.0%, P = 0.017). There were no significant differences in the total fiber number in the superficial and deep regions between the two quail lines (P = 0.718). The HW quail line showed a larger mean fiber cross-sectional area (CSA; 375.5 v. 176.6 μm², P < 0.001) and type IIA fiber CSA (243.7 v. 131.9 μm², P < 0.001) than the RBC quail line. The HW line also had greater CSA percentage (60.2% v. 34.2%, P < 0.001) and number percentage (41.6% v. 14.2%, P < 0.001) of type IIB fibers, although there were no significant differences in type IIB fiber CSA between the RBC and HW lines (P = 0.219). Therefore, greater body and muscle weights of the HW line are caused by differences in muscle fiber characteristics, especially the proportion of type IIB fiber and the CSA of type IIA fiber, compared with the RBC line. The results of this study suggest that muscle fiber hypertrophy has more impact on body and muscle weights of the different quail lines than muscle fiber hyperplasia.     

Histology, immunocytology, histochemistry and muscle fiber innervation of the pectoralis major and supracoracoideus muscles of Excalfactoria chinensis chinensis (L.)]

The morphology of the pectoralis major muscle and its antagonist, the supracoracoideus muscle, of the Chinese quail was studied in comparison with the Japanese quail, in relation to behavioral characteristics. The actomyosin ATPase reaction after alkaline and acid preincubation reveals two fibre types. The indirect immunofluorescence, using specific antibodies against 'slow' (twitch) myosin from the human vastus lateralis muscle, provokes a weak reaction. All fibres observed show focal, monoaxonal 'en plaques' endings, typical of the phasic motor system. For the two quail species, the muscle structure seems adequate in relation to the movement characteristics, meaning muscle activity of migratories, flying long distances.     

Combined diffusion and strain tensor MRI reveals a heterogeneous, planar pattern of strain development during isometric muscle contraction

The purposes of this study were to create a three-dimensional representation of strain during isometric contraction in vivo and to interpret it with respect to the muscle fiber direction. Diffusion tensor MRI was used to measure the muscle fiber direction of the tibialis anterior (TA) muscle of seven healthy volunteers. Spatial-tagging MRI was used to measure linear strains in six directions during separate 50% maximal isometric contractions of the TA. The strain tensor (E) was computed in the TA's deep and superficial compartments and compared with the respective diffusion tensors. Diagonalization of E revealed a planar strain pattern, with one nonzero negative strain (ε(N)) and one nonzero positive strain (ε(P)); both strains were larger in magnitude (P < 0.05) in the deep compartment [ε(N) = -40.4 ± 4.3%, ε(P) = 35.1 ± 3.5% (means ± SE)] than in the superficial compartment (ε(N) = -24.3 ± 3.9%, ε(P) = 6.3 ± 4.9%). The principal shortening direction deviated from the fiber direction by 24.0 ± 1.3° and 39.8 ± 6.1° in the deep and superficial compartments, respectively (P < 0.05, deep vs. superficial). The deviation of the shortening direction from the fiber direction was due primarily to the lower angle of elevation of the shortening direction over the axial plane than that of the fiber direction. It is concluded that three-dimensional analyses of strain interpreted with respect to the fiber architecture are necessary to characterize skeletal muscle contraction in vivo. The deviation of the principal shortening direction from the fiber direction may relate to intramuscle variations in fiber length and pennation angle.     

Analysis of vertebral muscle obtained during surgery for correction of a lumbar disc disorder

Biopsies of erector spinae (sacrospinalis) and multifidus muscles were taken, in a precise manner, adjacent to lumbar vertebra 5, from 18 patients aged 28-73, suffering from acute lumbar disc disorders. The respective muscle fiber characteristics were assessed histologically and histochemically using ATPase and NADH staining procedures. A 'strength factor' component was developed for each muscle by combining measurements of fiber area and fiber type, to introduce a functional indication of force. No obvious signs of muscle pathology were evident histologically or histochemically. While a large difference in muscle characteristics may exist on opposite sides of the vertebral column in individual subjects, these differences do not appear to be related to the side of the disc protrusion. It is therefore suggested that muscle obtained from patients suffering from disc protrusion can be used as representative of normal muscle.