White Muscle Fibres Research Articles

Dual motor innervation in the axial musculature of fishes

A systematic survey of motor innervation in the myotomal muscle fibres in several groups of fishes was conducted to observe the extent of dual innervation, a phenomenon found within those myotomal muscle fibres with terminal innervation. It is concluded that the dually innervated myotomal muscle fibre is a primitive vertebrate feature. Furthermore, it is suggested that this particular form of polyneuronal innervation is retained in the course of neural evolution within the homogeneous white myotomal muscle fibre region in these fish groups in order to insure synchrony of firing during sudden, rapid locomotion. The findings are examined in light of current ideas regarding the direct adrenergic innervation in addition to cholinergic innervation of striated muscle fibres.

The effect of electrical stimulation, fasting and anesthesia on the carnitine(s) and acyl-carnitines of rat white and red skeletal muscle fibres

1. 1. Time courses for the effect of electrical stimulation, fasting and sampling mode (anesthesia vs decapitation) on the quantitative distribution of carnitine and its esters in fast white and fast red skeletal muscle fibres of rats were determined. 2. 2. Both fibre types responded similarly to electrical stimulation with respect to changes in acetyl- and propionylcarnitine, but the time course was very different. 3. 3. The proportion of esterified carnitine decreased with fasting and anesthesia in both fibres compared to the fed decapitated group. 4. 4. This shift in the acylation state of carnitine was mainly due to the decrease of acetylcarnitine levels. 5. 5. The data show that the use of anesthetics may induce significant quantitative changes in specific acylcarnitine levels, presumably reflecting changes in specific acylcoenzyme A levels.

Acetylcholinesterase and acetylcholine receptor histochemistry on end plate regions, myotendinous junctions, and sarcolemma in the axial musculature of three teleost fish species

In this paper we describe a rapid procedure for the identification of motor end plates in fish. We demonstrated the presence of acetylcholine receptors by means of an immune fluorescence technique with alpha-bungarotoxin. Koelle's thiocholine method was used to localize acetylcholinesterase (AChE) activity. Under carefully controlled conditions the AChE activity and the anti-alpha-bungarotoxin fluorescence showed an equal distribution. This means that in the study of motor innervation in fish the AChE reaction can be used to stain only the motor end plates, leaving the AChE rich preterminal axons unstained. Comparison of the AChE reaction pattern with the distribution of binding sites for antibodies raised against neurofilament protein revealed that in end plate regions high concentrations of AChE are only present in axons and end plates. The myotendinous junctions also possess a high receptor density and enzyme activity. A low enzymatic activity was found at the non-junctional periphery of white muscle fibres. This activity probably resides in the sarcolemma. No non-specific cholinesterase activity was found. From light microscopical analysis it appeared that a single end plate may innervate 2 adjacent muscle fibres. This was affirmed by ultrastructural observations. The dual innervation suggests that, in fish, motor units have a limited distribution through the myotome.

Changes in the satellite cells of the anuran tadpole tail muscles during metamorphosis.

The incidence and the ultrastructure of the satellite cells associated with red and white muscle fibres of the anuran (Rana japonica) tadpole tail were examined in three stages (hindlimb-bud, prometamorphic, and climax) during metamorphosis. In these three stages the satellite cells are found more frequently in the red fibres than in the white fibres. As metamorphosis proceeds, the incidence of the satellite cells decreases in both red and white fibres. The satellite cells in the hindlimb-bud stage have abundant cytoplasm rich in organelles. Cisternae of rough endoplasmic reticulum are often dilated. The intercellular space between the satellite cell and the muscle fibre is narrow and relatively constant (15-25 nm). Some satellite cells appear to be in the process of fusion with the muscle fibre. Cytoplasmic volume and organellar content are gradually reduced during metamorphosis. In the prometamorphic and climax stages, the intercellular space is in general gradually extended. It often exceeds 0.5 microns, and usually contains the basal lamina and fibrous materials. Some satellite cells have cytoplasmic processes that project into the interstitial space through a gap in the basal lamina.

The effect of glucocorticoid treatment on denervated rat hemidiaphragm

The degenerative process in phrenic nerve motor nerve terminals following nerve section was analyzed in rats that had previously been subjected to an intensive short term regimen of the steroid preparation triamcinolone. Morphological studies indicated that the onset time of degeneration was similar to that of untreated rats but less severe, and the time for maximal degenerative changes was increased. Concurrent to the preservation of motor nerve terminal structure under conditions of denervation, triamcinolone also induced myopathies in the diaphragm, the white muscle fibers being predominantly affected. Due to the structural aberrations of muscle, the indirect and direct twitch response of hemidiaphragms in triamcinolone treated rats was depressed. Data obtained from indirect post-tetanic potentiation (PTP) responses, however, did express the anatomical preservation of motor nerve terminals. These findings may add support to previous observations for the basis of effectiveness of the glucocorticoids in the treatment of neuromuscular disorders.

Effects of immobilization and partial denervation on the differentiation of muscle fiber types in the Zebrafish, Brachydanio rerio.

In this study we tested the effects of immobilization and of spinal cord lesion on the differentiation of muscle fiber types in the myotomal muscle of the zebrafish. We found that the differentiation of embryonic red and white muscle fibers occurs in immobilized as well as in denervated myotomes of zebrafish embryos. Intermediate and adult red muscle fibers are not formed in denervated myotomes of larvae. Adult zebrafishes with spinal cord lesions in the anal region show abnormal undulating movements in the rostral part of the body. This change in muscle activity correlates with an increase in the number of intermediate scattered fibers. We conclude that direct contact with spinal cord motorneurons is not necessary for the differentiation of embryonic red and white fibers. The differentiation of intermediate muscle fibers is under extrinsic control. The factors that determine the formation of adult red fibers are not yet clear.

Energetic advantages of burst-and-coast swimming of fish at high speeds.

A theoretical model describes how an intermittent swimming style can be energetically advantageous over continuous swimming at high average velocities. Kinematic data are collected from high-speed ciné pictures of free swimming cod and saithe at high velocities in a burst-and-coast style. These data suggest that fish make use of the advantages shown by choosing initial and final burst velocities close to predicted optimal values. The limiting role of rapid glycogen depletion in fast white anaerobic muscle fibres is discussed.

Heterogeneity of contractile proteins. Differences in tropomyosin in fast, mixed, and slow skeletal muscles of the rabbit.

The subunit composition and dimeric species of tropomyosin with respect to its alpha and beta subunits have been analyzed from several physiologically different types of skeletal muscle of the rabbit using one- and two-dimensional gel electrophoresis. The findings indicate that there are two types of tropomyosin distributions in rabbit muscles: one in which alpha 2 is the prevalent species and another in which alpha beta is prevalent. While the alpha 2-prevalent pattern is characteristic of some fast muscles, notably longissimus dorsi and psoas, it is not the only pattern found in fast muscles. Plantaris, which is histochemically indistinguishable from longissimus dorsi, exhibits an alpha beta-prevalent distribution. This observation shows that there are at least two types of fast white muscle fibers which differ in their tropomyosin composition and species. The alpha beta-pattern is also found in fast red, slow, and mixed muscles. The fast and slow alpha beta-prevalent patterns can be distinguished electrophoretically because of heterogeneity of their subunits. Finally, the relative abundance of the different forms of tropomyosin in each of the muscles studied indicates that the tropomyosin dimer does not assemble randomly from alpha and beta subunits, but that alpha beta is assembled preferentially in vivo.

A Comparative Study of Fibre Type Characteristics and Terminal Innervation in Head and Axial Muscle of the Carp (Cyprinus Carpio L.) : a Histochemical and Electron-Microscopical Study

In the axial muscles and in a head muscle (m. hyohyoideus) of the carp two slow (red) and three fast (white, large pink and small pink) fibre types were distinguished on the basis of reactions with antisera, the pH stability of ATPase and succinatedehydrogenase activity. The gradual transition in histochemical characteristics between small and large pink fibres and the occurrence of stadia intermediate between myosatellite cells and small muscle fibres suggest that the small fibres are a growth stage. Density of nerve terminations was highest on red fibres, which is in accordance with physiological data. White axial muscle fibres had the lowest termination density. Pink fibres of the m. hyohyoideus had significantly more terminations per millimeter fibre length than pink fibres of the axial muscles. Vesicle densities per endplate profile and per synaptic contact were similar in all types. Endplates on white fibres had narrower synaptic clefts and vesicles that were slightly more elliptical than those on other types. The presence of swollen mitochondria in endplates on red head muscle fibres may reflect the continuous rhytmic activity of these fibres. The absence of subjunctional folds on slow as well as on fast fibres suggest that endplates on both types release but little acetylcholine per stimulus.

An ultrastructural and histochemical study of the axial musculature in the African lungfish.

Red, intermediate, and white axial muscle fibres of African lungfish were studied using histochemical techniques and electron microscopy. Gross dissection revealed the presence of a small wedge of red coloured muscle along the lateral line. This wedge was shown by histochemical demonstrations of lactate and succinate dehydrogenases, of adenosine triphosphatases, and of lipid to be composed of a mosaic of red and intermediate fibres measuring 23.63 and 34.30 micrometer in average diameter, respectively. The bulk of the myotome was composed of white fibres having an average diameter of 67.35 micrometer. Mitochondrial density, capillarity and lipid content were very low for all fibres. These data suggest that the axial musculature is geared primarily for anaerobic function. The mosaic arrangement of fibres, and the lack of a subsarcolemmal band of mitochondria suggests that the lungfish have a muscle organisation that is transitional between lower vertebrates and amphibians.

Effects of long-term administration of ambenonium chloride on motor end-plate fine structure and acetylcholine receptor in rat

Ambenonium chloride was administered orally in a dosage of 6 mg/kg/day to rats for 14–360 days. Motor end-plate fine structure and junctional AChR were quantitatively analyzed in red (soleus) and white (EDL) muscle fibers. In treated animals, degeneration and simplification of postsynaptic folds and widening of synaptic clefts were often observed in soleus end-plates, but infrequently in EDL end-plates. On the other hand, the postsynaptic AChR was reduced markedly in both soleus and EDL end-plates. No presynaptic changes were observed. These results show that long-term administration of Anti-ChE agents in myasthenia gravis may have an adverse effect on neuromuscular transmission.

Effect of denervation on the levels and rates of synthesis of specific enzymes in “fast-twitch” (breast) muscle fibers of the chicken.

It has been well documented that neural information, or the consequences of it, is required for the full phenotypic expression of different skeletal muscle fiber types. In the present work, we investigate the effect of removal of neural information, via surgical denervation, on the levels and rates of synthesis of several enzyme in mature breast ("fast-twitch") "white" muscle fibers of the chicken. Denervation of these muscles resulted in reductions in the concentrations of several glycolytic enzymes to new steady state levels which were only about 50% of normal, and these decreases in enzyme levels were completed within 2 weeks after severing the nerves. In contrast, denervation for as long as 6 weeks did not have a significant effect on the levels of creatine-P kinase molecules in this muscle type. The decreased level of the skeletal muscle-specific aldolase A4 isoenzyme in denervated breast muscle fibers was associated with a 2- to 3-fold reduction in the relative rate of synthesis of this enzyme following denervation. As expected, denervation had no appreciable effect on the relative rate of synthesis of the muscle-specific MM isoenzyme of creatine-P kinase in this muscle. Our results show that neural information, or the consequences of it, is required to maintain the levels and rates of synthesis of glycolytic enzymes but not of creatine-P kinase in mature fast-twitch muscle fibers. We suggest that denervation results in a partial "dedifferentiation" of these fibers.

Vascularization of the lateral muscle of some elasmobranchiomorph fishes

The vascular bed of the locomotor muscle in three shark species and in a holocephalan is investigated and the capillarization quantified by morphometrical methods. The red muscle fibres of Scyliorhinus, Galeus, Etmopterus and Chimaera are well vascularized having respectively 25, 18, 23 and 5 per cent of fibre surface covered by capillaries. The white muscle fibres of Scyliorhinus are far better vascularized than white muscle fibres of Galeus, Etmopterus and Chimaera. The fibre surface covered by capillaries are 9, 1.4, 0.2 and 1.3 per cent, respectively. The intermediate muscle fibres have a vascular supply between that of red and white muscle fibres in all species. If the capillary contact area to the fibres are related to the mitochondrial volume, more similar values are obtained for the vascular supply to all fibres types in all animals. This parameter indicates that there is a definite relation between the capacity of the oxygen transport system and the aerobic metabolic machinery.

Quantitative analysis of muscle breakdown during starvation in the marine flatfish Pleuronectes platessa.

The present study describes the effects of starvation for a duration of four months on the ultrastructure of skeletal muscles from the marine flatfish (Pleuronectes platessa L.). Starvation is associated with a decrease in resting metabolic rate from 20.1 +/- 2.2 to 11.6 +/- 1.5 mg . O2/kg/h (P less than 0.05) and muscle wasting. Median fibre size fell from 700 micrometer 2 to 500 micrometer 2 in intermediate (fast oxidative) and from 1,800 micrometer 2 to 600 micrometer 2 in starved, white (fast-glycolytic) muscle fibres. In contrast, median fibre size in red (slow oxidative) muscle remained within the range 300-400 micrometer 2. The fraction of red fibre volume occupied by myofibrils (58.6%) and mitochondria (24.5%) did not change significantly with starvation. There was, however, a decrease in stored lipid 110.7% to 3.2%) and an alteration in the structure of the cristae in mitochondria from red muscle. Atrophy of white muscle fibres is associated with a decrease in both the diameter and fractional volume occupied by myofibrils (85.7% to 61.9% P less than 0.01). In a high proportion of white fibres peripheral degeneration of Z-discs is evident causing an unravelling of the thin filament lattice. It is suggested that this allows a partial decrease in myofibril diameter and hence the maintenance of contractile function in muscle from starved fish. In severely degenerating white fibres, disorganised thick and thin filaments and numerous multi-membrane lysosome-like vesicles are observed. Starvation results in an increase in the average content of mitochondria in white fibres from 2.2 to 6.7% (P less than 0.01). In fed plaice mitochondria constitute less than 1% of the volume of the white fibre in 43.5% of the fibres. The proportion of white fibres containing more than 6% mitochondria increases from 6.5% to 58% with starvation.

Abnormal myosin heavy chain variant associated with avian muscular dystrophy.

Avian muscular dystrophy is characterized by the degeneration of fast white skeletal muscle fibers, with onset during development. Using a one-dimensional peptide mapping technique, we have detected two forms of the myosin heavy chain in the fast white fibers of adult domestic chickens, one form characteristic of birds homozygous for muscular dystrophy, the other of their normal controls. Four dystrophic strains carrying the same gene for muscular dystrophy were examined. No differences were detected in the embryonic heavy chain peptide maps of normal and dystrophic chickens, consistent with the developmental onset of the condition. Differences were also absent from the peptide maps of heavy chains from slow red fibers, which are unaffected in dystrophy. No dystrophy-specific peptide map differences were detected in the three light chains. Analysis of peptide maps of rod and the heavy chain component of subfragment-1 from normal and dystrophic heavy chains indicates the presence of amino acid sequence differences in the two proteins.

The effect of beta-receptor blockade on adrenaline-induced changes in redox and energy state in m. vastus lateralis and m. soleus of the rat in vivo.

The metabolic changes in blood, red (m. soleus) and white (m. vastus lateralis) skeletal muscle fibres were investigated after short-term (3 min) infusion of adrenaline with or without prior treatment with propranolol or metoprolol. The adrenaline-induced increase in plasma lactate levels was totally prevented by prior treatment with metoprolol or propranolol, whilst the beta-blockers had no effect on blood glucose levels. Similar effects on lactate levels were found in the m. soleus, while metoprolol was less effective than propranolol in m. vastus lateralis. Adrenaline decreased the level of muscle creatinine phosphate and ADP, causing the equilibrium of the creatinine kinase reaction to change in the direction of ATP synthesis, although the level of ATP usually decreased. This effect was more pronounced in m. vastus lateralis compared with m. soleus. The [ATP]/[ADP] [Pi]-ratio tended to increase during infusion of adrenaline. This effect was counteracted by metroprolol but not by propranolol. The effects on the "phosphate potential" ([ATP]/[ADP] [Pi]) and the equilibrium within the creatine kinase were more pronounced in m. vastus lateralis than in m. soleus. The results demonstrate the possible role of receptors other than beta-receptors, i.e. alpha-receptors, in mediating changes in plasma glucose levels, while plasma lactate levels are regulated by the beta-adrenergic system. The role of beta-receptors in mediating changes in muscle lactate levels may differ in m. soleus and m. vastus lateralis, with a relative predominance of beta 2-receptors in m. vastus lateralis. Quantitative and qualitative differences in the adrenergic control of the energy state in the two types of muscle fibre were obvious, although it was not possible to distinguish clearly between the relative importance of alpha, beta 1 and beta 2-receptors.

Distribution of CAIII in fetal and adult human tissue.

Carbonic anhydrase III (CAIII), an enzyme recently shown by conventional electrophoresis to be muscle specific, has been qualified by "rocket" immunoelectrophoresis. This more sensitive technique has shown that the enzyme is virtually specific to skeletal muscle, where it occurs at a level of 5 mg per g, with trace levels in smooth muscle, cardiac muscle, and lung. In man there does not appear to be any correlation between CAIII levels and the proportion of red and white muscle fibers. The fetal development of CAIII has also been examined using immunoelectrophoresis, and the enzyme can be detected at 11 weeks' gestation. The CAIII level rises gradually up to 25 weeks, and there is then a more dramatic increase to reach approximately half adult level at birth.

Studies on the nature of the Z‐discs in skeletal muscle fibres of sharks, Etmopterus spinax L. and Galeus melastomus Rafinesque‐Schmaltz

The ultrastructural details of Z‐discs from red, intermediate, and white axial muscle fibres from the sharks Etmopterus spinax and Galeus melastomus are described. Red fibre Z‐discs contain the most amorphous matrix material, and are thicker (100–115 nm) than intermediate (85–88 nm) and white Z‐discs (75–80 nm). Four sets of oblique bars extend tangentially from each thin filament. In each set two bars are present, those of white fibres are close together (approximately 5 nm), while those of red fibres are separated by a distance of 15 nm. A model of shark Z‐disc structure is proposed. The denaturation (heat transition) temperatures of the muscle proteins were studied by differential scanning calorimetry (DSC). The heat transitions of collagen, actin, and myosin were identified; the actin heat transition temperature increased in the sequence red, intermediate, and white. The total protein pattern of red and white muscle were studied by SDS electrophoresis. A protein with a molecular weight of about 55000 may represent a Z‐disc protein.

Suxamethonium fasciculations: a topographical study.

It has been found in a group of 455 gynaecological patients that not all the voluntary muscles of the body respond to suxamethonium in the same way. One group of muscles (e.g. biceps) which is sensitive to suxamethonium, responds by fasciculating in almost every individual. A second, resistant, group of muscles (e.g. pectoralis major) is almost totally unresponsive to suxamethonium. A third muscle group (e.g. triceps) shows fasciculations in about 60% of cases and appears intimately associated with the development of suxamethonium pains, for if fasciculations do occur then suxamethonium pains are likely to ensure, but not necessarily involving all the fasciculating muscles. A theory to account for these different groups has been proposed involving the known variation in distribution of red and white muscle fibres throughout the body.

Myofibrous organization of M. trapezius of crab-eating monkey

In order to clarify the functional characteristics of M. trapezius of monkey, the myofibrous organization of the 10 right muscles of adult crab-eating monkeys (4 males and 6 females) were examined, noting the number and the size of red and white muscle fibers, which were differentiated by Sudan-Black B staining method.The following results were obtained.1. The number of muscle fibers per sg. mm. was the largest in intermediate part of M. trapezius, and was larger in females than in males.2. The number of white muscle fibers was about 30-45% of the total number of muscle fibers, and which was larger in caudal part than in cranial part of M. trapezius and larger in males than in females.3. Concerning the size of muscle fibers, it was general to be larger in males than in females, and the size of white muscle fibers was always larger than the red muscle fibers. And the size of muscle fibers was the largest in caudal part, and was correlated with the muscle weight positively.4. The muscle fiber density was about 70% in each of 3 parts, and was the lowest in cranial part of muscle. The density of white muscle fibers occupied half or more of the total muscle fibers.5. From these results, it was considered that the myofibrous organization of M. trapezius was most developed in caudal part, and this tendency was predominant in males than in females and also in white muscle fibers than in red muscle fibers. These findings suggest that the characteristics of myofibrous organization of M. trapezius concur with the characteristics of locomotion of monkey.