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1
Kernell, Daniel. "Muscle Regionalization." Canadian Journal of Applied Physiology 23, no. 1 (February 1, 1998): 1–22. http://dx.doi.org/10.1139/h98-001.
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In this review, the term muscle fibre regionalization signifies the presence of regional intramuscular differences in fibre type composition. As is well known, highly regionalized muscles commonly have greater concentrations of slow fibres deep than superficially. However, the degree of regionalization varies markedly between muscles and is not confined to deep vs. superficial locations. Fibres of the same myosin type may show regionalized differences in their metabolic enzyme activity, even within single motor units (Larsson, 1992). Regionalization of fibre type composition occurs also within single neuromuscular partitions. The intraspinal position of motoneurones is often coarsely related to the intramuscular sites of their muscle units. Muscles with a marked fibre type regionalization tend to show a corresponding regionalization of activity; in several muscles, however, the activity regionalization may vary depending on the motor task. During early development, fibre type regionalization emerges even under aneural conditions. The mechanisms are still unknown; relevant aspects of early development are briefly reviewed. Key words: skeletal muscle, fiber type, topography, activity, development
2
Velotto, Salvatore, Ettore Varricchio, Maria Rosa Di Prisco, Tommaso Stasi, and Antonio Crasto. "Effect of Age and Sex on Histomorphometrical Characteristics of Two Muscles of Laticauda Lambs." Acta Veterinaria Brno 79, no. 1 (2010): 3–12. http://dx.doi.org/10.2754/avb201079010003.
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The aim of the present experiment was to determine the effect of sex and age on histochemical and morphometric characteristics of muscle fibres (myocytes) in lambs born by single, twin, triplet and quadruplet birth. Thirty lambs were slaughtered at 60 days of age; thirty were weaned at 60 days and fed until 120 days with flakes (60%) and food supplements, and then slaughtered. Muscle tissues were obtained from two muscles, namely m. semitendinosus and m. longissimus dorsi of all lambs. For each fibre type, area perimeter and diameter (maximum and minimum) were measured and slow-twitch oxidative fibres, fast-twitch glycolytic fibres, fast-twitch oxidative-glycolytic fibres were histochemically differentiated. The muscles were stained for myosin ATPase, and succinic dehydrogenase. At 60 days, females had fibres larger than males, whereas the opposite was observed at 120 days. Besides, at 60 days, the lambs born by single birth had fibres larger than those born by multiple birth, whereas the opposite was observed at 120 days. Single lambs were heavier than twin lambs and multiple lambs. Fast-twitch glycolytic fibres had the largest size, followed by slow-twitch oxidative and fast-twitch oxidative glycolytic fibres. The dimensions of fibre types in m. longissimus dorsi were larger than in m. semitendinosus (P < 0.001).These muscle fibre characteristics are thought to be important factors influencing meat quality, which is often related to metabolic and contractile properties as determined by the muscle fibre type distribution.
3
Neil, D. M., W. S. Fowler, and G. Tobasnick. "MYOFIBRILLAR PROTEIN COMPOSITION CORRELATES WITH HISTOCHEMISTRY IN FIBRES OF THE ABDOMINAL FLEXOR MUSCLES OF THE NORWAY LOBSTER NEPHROPS NORVEGICUS." Journal of Experimental Biology 183, no. 1 (October 1, 1993): 185–202. http://dx.doi.org/10.1242/jeb.183.1.185.
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The myofibrillar proteins in fibres from the abdominal flexor muscles of the Norway lobster, Nephrops norvegicus, have been identified using SDS-PAGE gel electrophoresis. Several contractile and regulatory proteins are expressed as multiple isoforms in single fibres and, according to these, one fast fibre phenotype (F) can be identified in the deep flexor muscles and two slow fibre phenotypes (S1 and S2) can be distinguished in the superficial flexor muscles. The two slow fibre phenotypes are distributed non-uniformly across the superficial flexor muscle, and in the lateral bundle there is a heterogeneous mixture of both S1 and S2 fibres. Using histochemical procedures applied to intact or freeze-dried fibres in conjunction with measurements of fibre sarcomere length and gel electrophoresis, an exact correspondence can be demonstrated between the morphological properties, enzymatic content and myofibrillar protein composition of individual fibres from the deep and superficial flexor muscles. In the superficial flexor muscle, fibres of the S1 phenotype have a mean sarcomere length of <8 micrometre, a low oxidative capacity and an acid-labile isoform of myosin ATPase, while fibres of the S2 phenotypes have a longer sarcomere length (mean >9 micrometre), a higher oxidative capacity and an acid-stable isoform of myosin ATPase. These results are discussed in terms of the relationships between the different muscle fibre properties and the usefulness of procedures applied to single fibres for determining them.
4
Velotto, Salvatore, Claudia Vitale, Tommaso Stasi, and Antonio Crasto. "New Insights into Muscle Fibre Types in Casertana Pig." Acta Veterinaria Brno 79, no. 2 (2010): 169–76. http://dx.doi.org/10.2754/avb201079020169.
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Little is known about the Casertana pig. The aim of this study was to evaluate the effect of sex on histochemical and morphometrical characteristics of muscle fibres (myocytes) in this pure breed and to verify the presence of giant fibres as well as vascularity of the muscle. Finally, maximum shortening velocity and isometric tension were measured in single muscle fibres. Sixteen Casertana pigs (8 males, 8 females) from a farm in Campania (Italy) were slaughtered at one year of age. Muscle tissues were obtained from psoas minor, rhomboideus and longissimus dorsi. Myofibres were stained for myosin adenosine triphosphatase, succinic dehydrogenase, and α-amylase-periodic acid schiff. For all fibre types, the area and perimeter were measured. Slowtwitch oxidative fibres, fast-twitch glycolytic fibres and fast-twitch oxidative-glycolytic fibres were histochemically differentiated; an image-analyzing system was used. The results showed significant differences between the sexes in the size of all three fibre types. The psoas minor muscle had a high percentage of slow-twitch oxidative fibres and contained more capillaries per fibre and per mm2 than rhomboideus and longissimus dorsi, in which fast-twitch glycolytic fibres dominated. The cross-sectional area of all fibre types was larger in longissimus dorsi than in rhomboideus and psoas minor muscles; the giant fibres were present in the longissimus dorsi muscle only. Besides, isometric tension values were higher in fast-twitch glycolytic fibres than in the other ones. Variations in fibre type composition may contribute to meat quality.
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Westwood, F. Russell, Alison Bigley, Kevin Randall, Alan M. Marsden, and Robert C. Scott. "Statin-Induced Muscle Necrosis in the Rat: Distribution, Development, and Fibre Selectivity." Toxicologic Pathology 33, no. 2 (February 2005): 246–57. http://dx.doi.org/10.1080/01926230590908213.
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Simvastatin and cerivastatin have been used to investigate the development of statin-induced muscle necrosis in the rat. This was similar for both statins and was treatment-duration dependent, only occurring after 10 days had elapsed even if the dose was increased, and still occurring after this time when dosing was terminated earlier as a result of morbidity. It was then widespread and affected all areas of the muscular system. However, even when myotoxicity was severe, particular individual muscles and some types of fibres within affected muscles were spared consistently. Fibre typing of spared muscles and of acutely necrotic fibres within affected muscles indicated a differential fibre sensitivity to statin-induced muscle necrosis. The fibres showed a necrotic response to statin administration that matched their oxidative/glycolytic metabolic nature: Least sensitive →I ↔ IIA ↔ IID ↔ IIB ← most sensitive. Type I and IIB fibres represent metabolic extremes of a continuum of metabolic properties through the fibre types with type I fibres most oxidative in metabolism and type IIB fibres most glycolytic. In addition, in some (nonnecrotic) glycolytic fibres from muscles showing early multifocal single fibre necrosis the only subcellular alterations present in isolation of any other changes were mitochondrial. These changes were characterised by an increased incidence of vacuolation and the formation of myelinoid vesicular bodies that accumulated in the subsarcolemmal areas. These findings suggest an important early involvement of mitochondria in selective glycolytic muscle fibre necrosis following inhibition of the enzyme HMG-CoA reductase.
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Gunzel, D., S. Galler, and W. Rathmayer. "FIBRE HETEROGENEITY IN THE CLOSER AND OPENER MUSCLES OF CRAYFISH WALKING LEGS." Journal of Experimental Biology 175, no. 1 (February 1, 1993): 267–82. http://dx.doi.org/10.1242/jeb.175.1.267.
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1. The closer and opener muscles in the third walking legs of the three crayfish Pacifastacus leniusculus, Procambarus clarkii and Astacus leptodactylus are composed of fibres which differ in histochemistry, electrophysiology and morphology. Three major groups of fibres (A, B and C) were distinguished. 2. Group A fibres react weakly to histochemical stains for myofibrillar ATPase (mATPase) activity characteristic of fibres with slow shortening speeds. In the opener muscle, they are innervated by the opener excitor (OE) and the specific opener inhibitor (OI). In the closer muscle, group A fibres are innervated by the common inhibitory neurone (CI) in addition to single (slow closer excitor, SCE) or double excitatory (SCE and fast closer excitor, FCE) innervation. Group A fibres have the largest excitatory junction potentials (EJPs), the longest membrane time constants (tau) and the longest sarcomeres. They are located at the very distal and proximal ends of both muscles. 3. Group B fibres show higher mATPase activity than group A fibres. In the opener muscle, they are innervated by OE and OI; in the closer muscle, they receive double excitatory (SCE and FCE) and CI innervation. Single SCE and OE EJPs are small; those caused by FCE are larger. tau is shorter than in the other two fibre groups. Sarcomere lengths lie between those of group A and C fibres. Group B fibres are found along the entire lengths of both muscles. 4. Group C fibres exhibit the highest mATPase activity (characteristic of fibres with fast shortening velocity) which, in contrast to the ATPase of group B fibres, is not resistant to alkaline preincubation at pH 10.05. In the closer, these fibres lack innervation by CI, otherwise the innervation pattern is identical to that of group B fibres. EJP size is similar to that of group B fibres; tau ranges between values for group A and B fibres. Sarcomere lengths are the shortest of all the fibre types. Group C fibres constitute the majority of the fibres in the two muscles and mainly occupy the central regions.
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Michael, Mena, Larisa Kovbasyuk, Paul Ritter, Michael B. Reid, Oliver Friedrich, and Michael Haug. "Redox Balance Differentially Affects Biomechanics in Permeabilized Single Muscle Fibres—Active and Passive Force Assessments with the Myorobot." Cells 11, no. 23 (November 22, 2022): 3715. http://dx.doi.org/10.3390/cells11233715.
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An oxidizing redox state imposes unique effects on the contractile properties of muscle. Permeabilized fibres show reduced active force generation in the presence of H2O2. However, our knowledge about the muscle fibre’s elasticity or flexibility is limited due to shortcomings in assessing the passive stress–strain properties, mostly due to technically limited experimental setups. The MyoRobot is an automated biomechatronics platform that is well-capable of not only investigating calcium responsiveness of active contraction but also features precise stretch actuation to examine the passive stress–strain behaviour. Both were carried out in a consecutive recording sequence on the same fibre for 10 single fibres in total. We denote a significantly diminished maximum calcium-saturated force for fibres exposed to ≥500 µM H2O2, with no marked alteration of the pCa50 value. In contrast to active contraction (e.g., maximum isometric force activation), passive restoration stress (force per area) significantly increases for fibres exposed to an oxidizing environment, as they showed a non-linear stress–strain relationship. Our data support the idea that a highly oxidizing environment promotes non-linear fibre stiffening and confirms that our MyoRobot platform is a suitable tool for investigating redox-related changes in muscle biomechanics.
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Sokoloff, A. J., and G. E. Goslow. "Neuromuscular organization of avian flight muscle: architecture of single muscle fibres in muscle units of the pectoralis (pars thoracicus) of pigeon (Columba livia)." Philosophical Transactions of the Royal Society of London. Series B: Biological Sciences 354, no. 1385 (May 29, 1999): 917–25. http://dx.doi.org/10.1098/rstb.1999.0443.
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The M. pectoralis (pars thoracicus) of pigeons ( Columba livia ) is comprised of short muscle fibres that do not extend from muscle origin to insertion but overlap ‘in-series’. Individual pectoralis motor units are limited in territory to a portion of muscle length and are comprised of either fast twitch, oxidative and glycolytic fibres (FOG) or fast twitch and glycolytic fibres (FG). FOG fibres make up 88 to 90% of the total muscle population and have a mean diameter one-half of that of the relatively large FG fibres. Here we report on the organization of individual fibres identified in six muscle units depleted of glycogen, three comprised of FOG fibres and three comprised of FG fibres. For each motor unit, fibre counts revealed unequal numbers of depleted fibres in different unit cross-sections. We traced individual fibres in one unit comprised of FOG fibres and a second comprised of FG fibres. Six fibres from a FOG unit (total length 15.45 mm) ranged from 10.11 to 11.82 mm in length and averaged (±s.d.) 10.74±0.79 mm. All originated bluntly (en mass) from a fascicle near the proximal end of the muscle unit and all terminated intramuscularly. Five of these ended in a taper and one ended bluntly. Fibres coursed on average for 70% of the muscle unit length. Six fibres from a FG unit (total length 34.76 mm) ranged from 8.97 to 18.38 mm in length and averaged 15.32 ±3.75 mm. All originated bluntly and terminated intramuscularly; one of these ended in a taper and five ended bluntly. Fibres coursed on average for 44% of the muscle unit length. Because fibres of individual muscle units do not extend the whole muscle unit territory, the effective cross-sectional area changes along the motor unit length. These non-uniformities in the distribution of fibres within a muscle unit emphasize that the functional interactions within and between motor units are complex.
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Jee, Hyunseok, and Jae-Young Lim. "Discrepancies between Skinned Single Muscle Fibres and Whole Thigh Muscle Function Characteristics in Young and Elderly Human Subjects." BioMed Research International 2016 (2016): 1–8. http://dx.doi.org/10.1155/2016/6206959.
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We aimed to analyse the mechanical properties of skinned single muscle fibres derived from the vastus lateralis (VL) muscle in relation to those of the whole intact thigh muscle and to compare any difference between young and older adults. Sixteen young men (29.25±4.65years), 11 older men (71.45±2.94years), 11 young women (29.64±4.88years), and 7 older women (67.29±1.70years) were recruited. In vivo analyses were performed for mechanical properties such as isokinetic performance, isometric torque, and power. Specific force and maximum shortening velocity (Vo) were measured with single muscle fibres. Sex difference showed greater impact on the functional properties of both the whole muscle (p<0.01) and single muscle fibres than aging (p<0.05). Sex difference, rather than aging, yielded more remarkable differences in gross mechanical properties in the single muscle fibre study in which significant differences between young men and young women were found only in the cross-sectional area and Vo (p<0.05). Age and sex differences reflect the mechanical properties of both single muscle fibres and whole thigh muscle, with the whole muscle yielding more prominent functional properties.
10
Staron, R. S., and D. Pette. "The multiplicity of combinations of myosin light chains and heavy chains in histochemically typed single fibres. Rabbit tibialis anterior muscle." Biochemical Journal 243, no. 3 (May 1, 1987): 695–99. http://dx.doi.org/10.1042/bj2430695.
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1. Combined histochemical and biochemical single-fibre analyses [Staron & Pette (1987) Biochem. J. 243, 687-693], were used to investigate the rabbit tibialis-anterior fibre population. 2. This muscle is composed of four histochemically defined fibre types (I, IIC, IIA and IIB). 3. Type I fibres contain slow myosin light chains LC1s and LC2 and the slow myosin heavy chain HCI, and types IIA and IIB contain the fast myosin light chains LC1f, LC2f and LC3f and the fast heavy chains HCIIa and HCIIb respectively. 4. A small fraction of fibres (IIAB), histochemically intermediate between types IIA and IIB, contain the fast light myosin chains but display a coexistence of HCIIa and HCIIb. 5. Similarly to the soleus muscle, C fibres in the tibialis anterior muscle contain both fast and slow myosin light chains and heavy chains. The IIC fibres show a predominance of the fast forms and the IC fibres (histochemically intermediate between types I and IIC) a predominance of the slow forms. 6. A total of 60 theoretical isomyosins can be derived from these findings on the distribution of fast and slow myosin light and heavy chains in the fibres of rabbit tibialis anterior muscle.
11
Lomax, R. B., and W. R. Robertson. "The effects of hypo- and hyperthyroidism on fibre composition and mitochondrial enzyme activities in rat skeletal muscle." Journal of Endocrinology 133, no. 3 (June 1992): 375—NP. http://dx.doi.org/10.1677/joe.0.1330375.
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ABSTRACT Hypo- and hyperthyroidism have been associated with changes in the activities of mitochondrial enzymes in homogenates of skeletal muscles, but it is unclear whether such changes were due to changes in single fibre enzyme activities or to previously documented changes in relative numbers of fibres. In this study the activities of the mitochondrial enzymes α-glycerol phosphate dehydrogenase (m-αGPDH) and succinate dehydrogenase (SDH) were measured in single fibres of the soleus and gastrocnemius muscles of the rat by cytochemical assays. In the soleus muscles of hypothyroid animals there was a decrease in the mean percentage (± s.d.) of type II fibres from 8·0 ± 6·0 to 0·8 ± 1·9% (P < 0·05) and decreases in SDH activities in all fibre types (P < 0·005). In the gastrocnemius muscles of these animals there were no changes in fibre composition but type IIB fibres had reduced (P < 0·05) m-αGPDH activities. In the hyperthyroid animals, in which body weight had increased relative to the euthyroid animals, there were increases in the percentages of type IC and type II fibres in the soleus from 4·3 ± 1·7 to 13·1 – 9·0% (P < 0·05) and from 9·6 ± 7·2 to 33·4 ± 9·6% (P < 0·005) respectively and an increase in the percentage of type IIA fibres in the gastrocnemius from 92·9 ± 2·3 to 97·0 ± 2·9% (P < 0·05). However, there were no increases in single fibre mitochondrial enzyme activities. It is therefore suggested that the administration of moderate, growth-promoting doses of thyroid hormones to euthyroid animals can cause changes in muscle fibre composition without stimulating the activities of mitochondrial enzymes. Journal of Endocrinology (1992) 133, 375–380
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DEGENS, Hans, Mattias SOOP, Peter HÖÖK, Olle LJUNGQVIST, and Lars LARSSON. "Post-operative effects on insulin resistance and specific tension of single human skeletal muscle fibres." Clinical Science 97, no. 4 (August 24, 1999): 449–55. http://dx.doi.org/10.1042/cs0970449.
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Surgery and accidental trauma are associated with a transient period of insulin resistance, substrate catabolism and muscle weakness. In the present study, we evaluated the changes in the force-generating capacity of chemically skinned single muscle fibres following abdominal surgery. Biopsies of the m. vastus lateralis were obtained in three patients 1 day before and 3 or 6 days after surgery. Part of the biopsy was frozen for histochemical analysis of the fibre cross-sectional area (FCSA) and myofibrillar protein content, and another part was used for single-fibre contractile measurements. All patients developed insulin resistance following surgery. The maximum velocity of unloaded shortening of single muscle fibres did not change following surgery. The FCSA did not decrease after surgery, as determined either from histochemical sections or from single fibres measured at a fixed sarcomere length of 2.76±0.09 μm (mean±S.D.). Further, the force-generating capacity of the single fibres, measured as maximal Ca2+-activated force (P0) or as P0 normalized to FCSA (specific tension), remained unchanged, as did the myofibrillar protein content of the muscle. In conclusion, the muscle weakness associated with post-operative insulin resistance is not related to a decreased specific tension or a loss of myofibrillar proteins. Other potential cellular mechanisms underlying post-operative weakness are discussed.
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Lakie, M., and LG Robson. "Thixotropy in frog single muscle fibres." Experimental Physiology 75, no. 1 (January 1, 1990): 123–25. http://dx.doi.org/10.1113/expphysiol.1990.sp003380.
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O'CONNELL, Brett, Long T. NGUYEN, and Gabriela M. M. STEPHENSON. "A single-fibre study of the relationship between MHC and TnC isoform composition in rat skeletal muscle." Biochemical Journal 378, no. 1 (February 15, 2004): 269–74. http://dx.doi.org/10.1042/bj20031170.
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In the present study, we investigated the possibility that MHC (myosin heavy chain) and TnC (troponin C) isoforms exist in specific combinations in rat-skeletal-muscle fibres. Single fibres (numbering 245) from soleus (predominantly slow-twitch) and sternomastoid (predominantly fast-twitch) muscles of adult rats were analysed for MHC and TnC isoform composition, using alanine-SDS/PAGE for separating MHC isoforms, and a novel method (based on the previously reported influence of Ca2+ on the mobility of Ca2+-binding proteins in SDS gels) for unequivocal identification of TnC isoforms in single-fibre segments. In this study, all fibres that contained only one MHC isoform (slow or fast) contained only the matching TnC isoform and all fibres that contained multiple fast MHC isoforms contained only the fast TnC isoform. Fibres expressing both slow and fast MHC isoforms displayed either both TnC isoforms or only one TnC isoform of a type depending on the relative proportion of fast/slow MHC present. Our results suggest a close relationship between MHC and TnC isoform composition in non-transforming skeletal muscles of adult rat.
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Biral, D., R. Betto, D. Danieli-Betto, and G. Salviati. "Myosin heavy chain composition of single fibres from normal human muscle." Biochemical Journal 250, no. 1 (February 15, 1988): 307–8. http://dx.doi.org/10.1042/bj2500307.
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Electrophoretic analysis in the presence of 33% glycerol of purified myosin from normal human muscle shows three distinct protein bands which are identified as type 1, 2B, and 2A myosin heavy chain (MHC) isoforms by affinity-purified polyclonal antibodies. Analysis of MHC of single human muscle fibres shows that human muscles contain a large population of fibres showing the coexistence of type 2A and 2B MHC.
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EL HAJ, A. J., and D. F. HOULIHAN. "In Vitro and In Vivo Protein Synthesis Rates in a Crustacean Muscle During the Moult Cycle." Journal of Experimental Biology 127, no. 1 (January 1, 1987): 413–26. http://dx.doi.org/10.1242/jeb.127.1.413.
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In vivo protein synthesis rates were measured in the carpopodite extensor muscle of the shore crab, Carcinus maenas, following a single, high-dose injection of [3H]phenylalanine, which stabilized specific radioactivities in the free pools. In intermoult animals the percentage of protein mass synthesized per day (the fractional rate of protein synthesis) was 1.15% day−1 for the whole extensor muscle. The small, slow-type tonic fibres in the extensor had fractional rates of protein synthesis some 2.1 times higher than those of the large, fast-type phasic fibres. Measurement of protein synthesis rates of extensor muscles from intermoult animals using an in vitro incubation over 2h gave fractional synthesis rates three times lower than those found in in vivo experiments. Compared with the intermoult animals, six- and three-fold increases in fractional synthesis rates were found in the extensor muscles from stages immediately preceding and following ecdysis, respectively. Microdissection of the muscle fibres revealed that the increased synthesis in postecdysial animals was occurring mainly at the external cuticular end of the muscle fibres. Autoradiographic analysis confirmed the cuticular end of the muscles as the major site of muscle protein synthesis. We conclude that the postecdysial increase in muscle fibre length and the associated increase in the sarcomere number is accompanied by an increase in protein synthesis in the muscles.
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Johnston, I. A., and Z. Horne. "Immunocytochemical investigations of muscle differentiation in the Atlantic herring (Clupea harengus: Teleostei)." Journal of the Marine Biological Association of the United Kingdom 74, no. 1 (February 1994): 79–91. http://dx.doi.org/10.1017/s0025315400035682.
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The myotomes in yolk-sac larvae of the Atlantic herring (Clupea harengus: Teleostei) contain a single layer of small-diameter superficial muscle fibres surrounding an inner mass of around 280 larger-diameter muscle fibres. The fraction of muscle fibre volume occupied by mitochondria is dependent on temperature, and in larvae reared at 8°C was 41% for the superficial fibres, and 25% for the inner muscle fibres. The inner muscle fibres of larvae share some myofibrillar proteins with adult white muscle, but contain unique isoforms of myosin heavy chains, troponin T, troponin I and myosin light chain 2. A monoclonal antibody has been produced which is specific to myosin light chain 3 (MLC3). Immunocytochemical studies have shown that the expression of MLC3 is switched off in the superficial muscle fibres at the start of metamorphosis when larvae reach 28–30 mm total length (TL). Metamorphosis to the juvenile stage is complete in fish 35–40 mm TL and is also associated with the development of gill filaments and the production of presumptive slow muscle fibres which form externally to the larval superficial muscle fibres in the region of the lateral line nerve.
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Rassier, Dilson E., Eun-Jeong Lee, and Walter Herzog. "Modulation of passive force in single skeletal muscle fibres." Biology Letters 1, no. 3 (June 28, 2005): 342–45. http://dx.doi.org/10.1098/rsbl.2005.0337.
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In this study, we investigated the effects of activation and stretch on the passive force–sarcomere length relationship in skeletal muscle. Single fibres from the lumbrical muscle of frogs were placed at varying sarcomere lengths on the descending limb of the force–sarcomere length relationship, and tetanic contractions, active stretches and passive stretches (amplitudes of ca 10% of fibre length at a speed of 40% fibre length/s) were performed. The passive forces following stretch of an activated fibre were higher than the forces measured after isometric contractions or after stretches of a passive fibre at the corresponding sarcomere length. This effect was more pronounced at increased sarcomere lengths, and the passive force–sarcomere length relationship following active stretch was shifted upwards on the force axis compared with the corresponding relationship obtained following isometric contractions or passive stretches. These results provide strong evidence for an increase in passive force that is mediated by a length-dependent combination of stretch and activation, while activation or stretch alone does not produce this effect. Based on these results and recently published findings of the effects of Ca 2+ on titin stiffness, we propose that the observed increase in passive force is caused by the molecular spring titin.
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Pette, D. "Metabolic heterogeneity of muscle fibres." Journal of Experimental Biology 115, no. 1 (March 1, 1985): 179–89. http://dx.doi.org/10.1242/jeb.115.1.179.
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Mammalian skeletal muscle is an extremely heterogeneous tissue. Its diversity results from a spectrum of fibres which are metabolically suited to a wide range of functional demands. As judged from enzyme activity analyses of single fibres, the metabolic properties of fibres belonging to the same motor unit are similar or identical. It is likely, therefore, that the phenotype expression of muscle fibres is primarily under neural control. Differences in recruitment patterns of various motor units explain the wide range of metabolic properties as evidenced by pronounced variations in enzyme activities and enzyme activity ratios. There exist large overlaps between the activity spectra of various enzymes of anaerobic and aerobic metabolism in slow- and fast-twitch fibres. Nevertheless, these two major fibre classes can be distinguished by discriminative enzyme activity ratios (e.g. phosphofructokinase/malate dehydrogenase, phosphofructokinase/3-hydroxyacyl-CoA dehydrogenase, fructose-1,6-diphosphatase/phosphofructokinase). Moreover, slow-twitch fibres display an H-type isozyme pattern of lactate dehydrogenase, whereas fast-twitch fibres are characterized by a predominance of LDH-5. No clear-cut differences exist between enzyme activity profiles and LDH isozyme patterns of the IIA and IIB subgroups of fast-twitch fibres. Comparative studies indicate that the metabolic properties of IIA and IIB fibres vary in different animal species. This observation supports the notion that metabolic and myosin-related properties of muscle fibres may be regulated independently. Due to relatively high turnover rates of enzymes of energy metabolism in muscle, changes in functional demands may be met by relatively rapid changes in metabolic properties. In view of these findings it is not surprising that muscle fibres display a spectrum of metabolic properties and represent stages within a dynamic equilibrium.
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ALTRINGHAM, J. D., and I. A. JOHNSTON. "Activation of Multiply Innervated Fast and Slow Myotomal Muscle Fibres of the Teleost Myoxocephalus Scorpius." Journal of Experimental Biology 140, no. 1 (November 1, 1988): 313–24. http://dx.doi.org/10.1242/jeb.140.1.313.
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A nerve-muscle preparation from the sculpin Myoxocephalus scorpius was used to study the membrane response of fast and slow muscle fibres to stimulation of the spinal nerves. There was no significant difference between resting potential in fast (−81.9mV) and slow fibres (−80.8mV). Fast fibres responded to a suprathreshold stimulus in the spinal nerve with an action potential. Overshoots of up to +32 mV were recorded. Both junction potentials and overshooting action potentials were observed in the slow fibres. The twitch/tetanus characteristics of myotomal muscle were investigated using isolated bundles of ‘live’ fast and slow fibres. Both fibre types responded to a single stimulus with a mechanical twitch. Fused tetani were obtained at around 50Hz in fast fibres and 20 Hz in slow fibres. In the slow fibres, tetanic tension increased with frequency up to around 50Hz. At frequencies giving maximum tetanic tension, the twitch/tetanus ratio was 0.70 for fast fibres and 0.29 for slow ones. These results are discussed with reference to the polyneuronal/multiterminal innervation pattern of the myotomal muscle in teleost fish and its role in locomotion.
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Essén–Gustavsson, B. "Metabolic responses of muscle to exercise." BSAP Occasional Publication 32 (2004): 1–9. http://dx.doi.org/10.1017/s0263967x00041185.
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AbstractMuscle is a tissue with a great plasticity due to the fact that it is composed of fibres having different contractile and metabolic properties. In horses, muscle metabolic responses to exercise are studied by taking biopsies from the gluteus medius muscle. Histochemical stains are used to identify slow contracting type I fibres and fast contracting type IIA and type IIB fibres and to evaluate fibre areas, capillary supply, oxidative capacity, glycogen and lipid content in a muscle. Biochemical analyses of substrates, metabolites and enzyme activities are performed either on a whole piece of muscle, on pools of fibres or on single fibres of identified type.All fibres contain glycogen whereas lipid is mainly found in type I and type IIA fibres that have smaller cross–sectional areas and a higher oxidative capacity than type IIB fibres. Large variations can be seen in metabolic profile between and within fibre types. The most common muscular adaptation to training is an increase in oxidative capacity, capillary density and an increase in the type IIA/IIB ratio. The order of recruitment of fibres during most types of exercise is from type I to type IIA and type IIB.The higher the intensity of exercise, the faster is the breakdown of glycogen. After racing (1640-2640m), and after high intense treadmill exercise, concentrations of lactate and inosine monophosphate (IMP) are increased in the muscle and concentrations of glycogen, adenosine triphosphate (ATP) and creatine phosphate (CP) decreased. Extremely low ATP and high IMP concentrations especially in some type II fibres are observed after racing.After exercise of low intensity and long duration glycogen and triglyceride stores in muscle are utilised, amino acid metabolism is enhanced and protein degradation may occur. After submaximal treadmill exercise to fatigue and after endurance rides glycogen is degraded and depletion occurs mainly in type I and type IIA fibres.Fibre type composition, substrate sources and differences in metabolic properties among fibres and the extent to which fibres are recruited are all factors that influence the metabolic responses of muscle to exercise. Biochemical analyses on whole muscle must be interpreted with caution since large variations in metabolic response to exercise occur among different fibres.
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Lutz, Gordon J., Shannon N. Bremner, Michael J. Bade, and Richard L. Lieber. "Identification of myosin light chains in Rana pipiens skeletal muscle and their expression patterns along single fibres." Journal of Experimental Biology 204, no. 24 (December 15, 2001): 4237–48. http://dx.doi.org/10.1242/jeb.204.24.4237.
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SUMMARY Isoforms of myosin heavy chain (MHC) and myosin light chain (MLC) influence contractile kinetics of skeletal muscle. We previously showed that the four major skeletal muscle fibre types in Rana pipiens (type 1, type 2, type 3 and tonic; amphibian nomenclature) contain four unique MHC isoforms. In the present study we defined the MLCs expressed in each of these R. pipiens fibre types. The MLC composition of single MHC-typed fibres was determined from western blots using a panel of monoclonal MLC antibodies. A total of seven MLCs were identified, including four types of MLC1, two of MLC2 and a single MLC3. Twitch fibre types (types 1, 2 and 3) expressed MLC1f and MLC2f, while tonic fibres contained a unique set of isoforms, MLC1Ta, MLC1Tb and MLC2T. MLC3 was expressed primarily in type 1, type 1-2 and type 2 fibres. Surprisingly, some frogs displayed a striking pattern of MLC expression where a unique isoform of MLC1 (MLC1x) was coexpressed along with the normal MLC1 isoform(s) in all fibre types. MLC1x was either expressed in all fibres of a given frog or was completely absent. The intraspecific polymorphism in MLC1 expression is likely to have a genetic basis, but is unlikely to be caused by allelic variation. The ratio of MLC3/MLC1 increased in direct proportion to the percentage of type 1 MHC, but was only weakly correlated. The variability in MLC3/MLC1 within a fibre type was extremely large. Both the MHC isoform and MLC3/MLC1 ratio varied significantly between 1 mm segments along the length of fibres. For all segments combined, MLC3/MLC1 increased with the percentage of type 1 MHC, but the correlation between segments was weaker than between fibres.
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Strateva, М., and G. Penchev. "Histological discrimination of fresh from frozen/thawed carp (Cyprinus carpio)." BULGARIAN JOURNAL OF VETERINARY MEDICINE 24, no. 3 (2021): 434–41. http://dx.doi.org/10.15547/bjvm.2019-0113.
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The aim of the study was to perform histological differentiation of dorsal and ventral musculature of fresh and frozen/thawed carps (Cyprinus carpio). Histological findings of muscle fibres (Myofibra striata) of fresh carps did not show any changes. Single freezing at –10 ºС resulted in extracellular gaps in the central part of some of fibres. After single freezing at –18 ºС, muscle fibres with cell destruction in the central part were identified while the periphery remained intact. Completely destructured and deformed areas of muscle fibres were demonstrated after single freezing at –27 ºС. Double freezing at –10 ºС resulted in shrinkage, extracellular gaps and fragmentation of fibres, while muscle fibres double-frozen at –18 ºС were impaired, degraded and with visible defects. The histological findings in carp muscle, double-frozen at –27 ºС comprised severely deformed muscle fibres with increased extracellular gaps from degraded muscle tissue. On the basis of findings, it could be concluded that double freezing of carps was not an appropriate method of storage and shelf-life extension.
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Wiens, T. J., Joanne Pearce, and C. K. Govind. "Neuromuscular properties of the quintuply innervated flexor muscle in lobster limbs." Canadian Journal of Zoology 69, no. 2 (February 1, 1991): 477–88. http://dx.doi.org/10.1139/z91-074.
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The flexor muscle of the lobster's walking leg was shown by enzyme histochemistry and electrophysiology to display a regional segregation of fibre types: medial fibres have a higher ATPase activity, lower oxidative capacity, and shorter membrane time constant than peripheral fibres lying near the cuticle. The muscle was confirmed to receive one inhibitory and four excitatory motor axons. As judged by the properties of their output excitatory junctional potentials (ejp's), the four excitors lie along the fast-to-slow gradient defined by the two specialized excitors of dually excited muscles. The Fα axon produces initially large ejp's which facilitate weakly or antifacilitate; they are similar to those of fast axons in other muscles. The Fρ axon at the other end of the spectrum produces strongly facilitating ejp's which are initially small, resembling those of known slow axons. The Fβ and Fγ axons show intermediate properties. The inhibitor, which is the common inhibitor of all leg muscles, innervates preferentially the more tonic muscle fibres, as does Fρ. Muscle fibres were observed to receive anywhere from one to five efferents, most receiving two to four. Serial electron microscopic observations in several regions revealed a rich supply of synaptic terminals, usually comprising a single inhibitory terminal and two or three excitatory ones. The inhibitory terminal typically has a few large synapses, each with more than one active site. Excitatory terminals, on the other hand, have many more smaller synapses, each with at least one active site. Although excitatory and inhibitory terminals were often closely juxtaposed, no synaptic interactions were observed between them.
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Staron, R. S., and D. Pette. "The multiplicity of combinations of myosin light chains and heavy chains in histochemically typed single fibres. Rabbit soleus muscle." Biochemical Journal 243, no. 3 (May 1, 1987): 687–93. http://dx.doi.org/10.1042/bj2430687.
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1. Six adult rabbit soleus muscles were analysed by isolating histochemically identified fibre pieces from freeze-dried serial cross-sections. 2. By the use of this method, four fibre types (I, IC, IIC and IIA) were identified and analysed micro-electrophoretically. 3. Type I fibres contained the slow myosin heavy chain HCI and the slow myosin light chains LC1s and LC2s. 4. Type IIA fibres contained the fast myosin HCIIa with the fast light chains and, in addition, either LC1s or both LC1s and LC2s. 5. The C fibres (IC and IIC) represented intermediate populations between types I and IIC (IC) and between IC and IIA (IIC). They contained varied ratios of HCI/HCIIa with both sets of fast and slow light chains. With regard to myosin composition and isoforms of other myofibrillar proteins (M- and C-proteins, alpha-tropomyosin, troponin I), IC fibres resembled type I and IIC fibres resembled type IIA. 6. The presence of various myosin light and heavy chains within a specific fibre suggests a multiplicity of isomyosins. Without consideration of LC1sa and LC1sb differences, at least 54 possible isomyosins can be derived: type I fibres contain one isomyosin, types IC and IIC 54 possible isomyosins, and type IIA up to 18.
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Crockford, T., I. Johnston, and B. Mcandrew. "Functionally significant allelic variation in myosin light chain composition in a tropical cichlid." Journal of Experimental Biology 198, no. 12 (December 1, 1995): 2501–8. http://dx.doi.org/10.1242/jeb.198.12.2501.
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Single fast muscle fibres in the tropical fish Oreochromis andersonii were found to contain two myosin light chains (LC1s; LC1f1* or LC1f2*). Breeding experiments confirmed that the different LC1s were of allelic origin and their inheritance patterns conformed to Mendelian expectations (1:2:1). The LC1s differed in apparent relative molecular mass by 800­900. No other differences in myosin subunits were found between the LC1 genotypes. The molar ratios of LC3:LC1(total) in the fast muscle of O. andersonii homozygous for LC1f1* or LC1f2* and heterozygous for both alleles were 2.0:1, 2.1:1 and 2.2:1, respectively, as determined by capillary electrophoresis. The maximum contraction velocity (Vmax) of single skinned muscle fibres was determined at 20 °C by the slack-test method. Vmax values (fibre lengths s-1) for fast muscle fibres from O. andersonii which were homozygous for either LC1f2* or LC1f1* were 5.3 and 3.3, respectively, compared with 3.8 when both alleles were present. Crosses between Oreochromis niloticus and O. andersonii produced F1 hybrids which were heterozygous for either LC1n/LC1f1* or LC1n/LC1f2*, where LC1n is the myosin light chain for O. niloticus. The distribution of myosin light chain genotypes in hybrid offspring was not significantly different from the expected Mendelian 1:1 ratio (47 %: 53 %). The Vmax (fibre lengths s-1) of muscle fibres containing LC1f2* from hybrid Oreochromis was 4.3 compared with 3.1 for the LC1f1* genotype. The results are consistent with a functionally significant allelic variation in myosin LC1 in fast muscle fibres from O. andersonii which is also expressed in hybrid genotypes.
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Delbono, O., and E. Stefani. "Calcium transients in single mammalian skeletal muscle fibres." Journal of Physiology 463, no. 1 (April 1, 1993): 689–707. http://dx.doi.org/10.1113/jphysiol.1993.sp019617.
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Berovic, N., N. Thomas, R. A. Thornhill, and J. M. Vaughan. "Observation of Brillouin scattering from single muscle fibres." European Biophysics Journal 17, no. 2 (June 1989): 69–74. http://dx.doi.org/10.1007/bf00257104.
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Hughes, S. M., J. M. Taylor, S. J. Tapscott, C. M. Gurley, W. J. Carter, and C. A. Peterson. "Selective accumulation of MyoD and myogenin mRNAs in fast and slow adult skeletal muscle is controlled by innervation and hormones." Development 118, no. 4 (August 1, 1993): 1137–47. http://dx.doi.org/10.1242/dev.118.4.1137.
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Each of the myogenic helix-loop-helix transcription factors (MyoD, Myogenin, Myf-5, and MRF4) is capable of activating muscle-specific gene expression, yet distinct functions have not been ascribed to the individual proteins. We report here that MyoD and Myogenin mRNAs selectively accumulate in hindlimb muscles of the adult rat that differ in contractile properties: MyoD is prevalent in fast twitch and Myogenin in slow twitch muscles. The distribution of MyoD and Myogenin transcripts also differ within a single muscle and correlate with the proportions of fast glycolytic and slow oxidative muscle fibres, respectively. Furthermore, the expression of a transgene consisting of a muscle-specific cis-regulatory region from the myoD gene controlling lacZ was primarily associated with the fast glycolytic fibres. Alteration of the fast/slow fibre type distribution by thyroid hormone treatment or by cross-reinnervation resulted in a corresponding alteration in the MyoD/Myogenin mRNA expression pattern. These findings show that the expression of specific myogenic helix-loop-helix regulators is under the control of innervation and humoral factors and may mediate differential control of contractile protein gene expression in adult muscle.
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Thompson, W. J., L. C. Soileau, R. J. Balice-Gordon, and L. A. Sutton. "Selective innervation of types of fibres in developing rat muscle." Journal of Experimental Biology 132, no. 1 (September 1, 1987): 249–63. http://dx.doi.org/10.1242/jeb.132.1.249.
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The technique of glycogen depletion has been used to identify the types of muscle fibres innervated by individual motor neurones in the neonatal rat. This analysis shows that neonatal motor units are highly biased in their fibre type composition, even at times when the fibres receive extensive polyneuronal innervation. This finding suggests that the innervation of muscle fibres is somehow sorted according to type during early development. This sorting does not appear to occur during the removal of the polyneuronal innervation because little, if any, increase in the bias of unit compositions occurs as the number of synapses present in the muscle is reduced 2- to 3-fold. To determine whether the sorted innervation might be explained by a selective synaptogenesis, a study was made of the type compositions of units formed by reinnervation of neonatal soleus muscle. Glycogen depletion of single units 2 weeks following crush of the soleus nerve at postnatal day 2 showed that most of them (10/12) had biased type compositions which could not be explained by a random reinnervation. The location of fibres in the reinnervated motor units suggests that the regenerating axons innervated a novel set of fibres. The differentiation of fibres into types was apparently not changed during their reinnervation. These results imply that regenerating motor neurones in the neonatal rat selectively reinnervate muscle fibre types. These and other studies further imply that the organization of fibres into motor units during normal development does not occur, as is widely believed, by a random innervation of naive fibres and their subsequent differentiation under the influence of innervation.
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Abrahams, V. C. "Group III and IV receptors of skeletal muscle." Canadian Journal of Physiology and Pharmacology 64, no. 4 (April 1, 1986): 509–14. http://dx.doi.org/10.1139/y86-083.
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The single largest group of sensory fibres leaving skeletal muscles are small myelinated or unmyelinated (groups III and IV) fibres. The receptors served by these small fibres have not been subjected to the same intensive study that receptors served by group I and II fibres have received. The evidence so far available suggests that receptors with group III and IV axons play a particular role in nociception and also subserve a wide range of sensory modalities. Despite their role in nociception, the primary afferent fibres from these receptors do not project to the substantia gelatinosa. A significant percentage of group III receptors are sensitive to stretch and have been thought to be the receptor source that initiates the clasp-knife reflex. Other group III receptors respond to chemical change within the muscle and have been implicated in the initiation of cardiovascular reflexes and the changes in muscle blood flow that accompany exercise. Group IV receptors also include high threshold mechanoreceptors and nociceptors. It is well known that encapsulated receptors are quite unevenly distributed within skeletal muscles and in different skeletal muscles. Preliminary evidence suggests that the variation in receptor content is not confined to encapsulated receptors, but that the receptors served by group III and IV afferents may have receptive properties that vary from muscle to muscle.
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Gydikov, A. A., and N. A. Trayanova. "Extracellular potentials of single active muscle fibres: Effects of finite fibre length." Biological Cybernetics 53, no. 6 (April 1986): 363–72. http://dx.doi.org/10.1007/bf00318202.
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DUBAS, F., and P. R. BOYLE. "Chromatophore Motor Units in Eledone Cirrhosa (Cephalopoda: Octopoda)." Journal of Experimental Biology 117, no. 1 (July 1, 1985): 415–31. http://dx.doi.org/10.1242/jeb.117.1.415.
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Innervation of chromatophore muscles of the octopus Eledone cirrhosa was investigated by stimulating nerve bundles in the skin with a suction electrode and monitoring chromatophore movements with a photo-cell or a video camera. Attention was focused on the organization of the chromatophore muscle fibres into motor units. Individual muscle fibres respond to single electrical impulses with twitch-like contractions that do not facilitate with repetition, but summate to a smooth tetanus at about 10–15 Hz. At tetanic frequency, the degree of expansion of single chromatophores is always maximal. However, the number of expanded chromatophores can be graded by variations of either the stimulus voltage or frequency. Individual chromatophores and probably individual muscle fibres are part of several motor units. Chromatophores forming a given motor unit are found among chromatophores served by other motor axons. The motor units apparently form precise parts of natural patterning.
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Azab, Azab. "Skeletal Muscles: Insight into Embryonic Development, Satellite Cells, Histology, Ultrastructure, Innervation, Contraction and Relaxation, Causes, Pathophysiology, and Treatment of Volumetric Muscle I." Biotechnology and Bioprocessing 2, no. 4 (May 28, 2021): 01–17. http://dx.doi.org/10.31579/2766-2314/038.
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Background: Skeletal muscles are attached to bone and are responsible for the axial and appendicular movement of the skeleton and for maintenance of body position and posture. Objectives: The present review aimed to high light on embryonic development of skeletal muscles, histological and ultrastructure, innervation, contraction and relaxation, causes, pathophysiology, and treatment of volumetric muscle injury. The heterogeneity of the muscle fibers is the base of the flexibility which allows the same muscle to be used for various tasks from continuous low-intensity activity, to repeated submaximal contractions, and to fast and strong maximal contractions. The formation of skeletal muscle begins during the fourth week of embryonic development as specialized mesodermal cells, termed myoblasts. As growth of the muscle fibers continues, aggregation into bundles occurs, and by birth, myoblast activity has ceased. Satellite cells (SCs), have single nuclei and act as regenerative cells. Satellite cells are the resident stem cells of skeletal muscle; they are considered to be self-renewing and serve to generate a population of differentiation-competent myoblasts that will participate as needed in muscle growth, repair, and regeneration. Based on various structural and functional characteristics, skeletal muscle fibres are classified into three types: Type I fibres, Type II-B fibres, and type II-A fibres. Skeletal muscle fibres vary in colour depending on their content of myoglobin. Each myofibril exhibits a repeating pattern of cross-striations which is a product of the highly ordered arrangement of the contractile proteins within it. The parallel myofibrils are arranged with their cross-striations in the register, giving rise to the regular striations seen with light microscopy in longitudinal sections of skeletal muscle. Each skeletal muscle receives at least two types of nerve fibers: motor and sensory. Striated muscles and myotendinous junctions contain sensory receptors that are encapsulated proprioceptors. The process of contraction, usually triggered by neural impulses, obeys the all-or-none law. During muscle contraction, the thin filaments slide past the thick filaments, as proposed by Huxley's sliding filament theory. In response to a muscle injury, SCs are activated and start to proliferate; at this stage, they are often referred to as either myogenic precursor cells (MPC) or myoblasts. In vitro, evidence has been presented that satellite cells can be pushed towards the adipogenic and osteogenic lineages, but contamination of such cultures from non-myogenic cells is sometimes hard to dismiss as the underlying cause of this observed multipotency. There are, however, other populations of progenitors isolated from skeletal muscle, including endothelial cells and muscle-derived stem cells (MDSCs), blood-vessel-associated mesoangioblasts, muscle side-population cells, CD133+ve cells, myoendothelial cells, and pericytes. Volumetric muscle loss (VML) is defined as the traumatic or surgical loss of skeletal muscle with resultant functional impairment. It represents a challenging clinical problem for both military and civilian medicine. VML results in severe cosmetic deformities and debilitating functional loss. In response to damage, skeletal muscle goes through a well-defined series of events including; degeneration (1 to 3days), inflammation, and regeneration (3 to 4 weeks), fibrosis, and extracellular matrix remodeling (3 to 6 months).. Mammalian skeletal muscle has an impressive ability to regenerate itself in response to injury. During muscle tissue repair following damage, the degree of damage and the interactions between muscle and the infiltrating inflammatory cells appear to affect the successful outcome of the muscle repair process. The transplantation of stem cells into aberrant or injured tissue has long been a central goal of regenerative medicine and tissue engineering. Conclusion: It can be concluded that the formation of skeletal muscle begins during the fourth week of embryonic development as specialized mesodermal cells, termed myoblasts, by birth myoblast activity has ceased. Satellite cells are considered to be self-renewing, and serve to generate a population of differentiation-competent myoblasts. Skeletal muscle fibres are classified into three types. The process of contraction, usually triggered by neural impulses, obeys the all-or-none law. VML results in severe cosmetic deformities and debilitating functional loss. Mammalian skeletal muscle has an impressive ability to regenerate itself in response to injury. The transplantation of stem cells into aberrant or injured tissue has long been a central goal of regenerative medicine and tissue engineering.
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ALTRINGHAM, J. D., and I. A. JOHNSTON. "Energy Cost of Contraction in Fast and Slow Muscle Fibres Isolated from an Elasmobranch and an Antarctic Teleost Fish." Journal of Experimental Biology 121, no. 1 (March 1, 1986): 239–50. http://dx.doi.org/10.1242/jeb.121.1.239.
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1. Single fast and small bundles of slow fibres were isolated from the muscles of an elasmobranch (dogfish, Scyliorhinus canicula) and an Antarctic teleost (Notothenia neglecta). A third fibre type present in the dogfish (superficial fibre) was also isolated. Fibres were chemically skinned with a non-ionic detergent. 2. Tension generation and ATPase activity were measured during isometric activations. ATPase activity was estimated by measuring the release of ADP into the experimental solutions using high performance liquid chromatography. 3. In the dogfish fibre types, both tension and ATPase activity increased in the order superficial < slow < fast, even after corrections were made for differences in myofibrillar density. The economy of isometric contraction (tension/ATPase activity) was 50–60% higher in the slow and superficial fibres than in the fast. 4. In the Antarctic species, both tension and ATPase activity of the fast fibres were higher than those of the slow fibres, and the slow fibres were 30% more economical than fast fibres. After correction for differences in myofibrillar density, tensions were very similar. 5. The results are discussed with reference to the energy supply, recruitment pattern and function of the various fibre types.
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Pollock-Tahiri, Evan, and Marius Locke. "The cellular stress response of rat skeletal muscle following lengthening contractions." Applied Physiology, Nutrition, and Metabolism 42, no. 7 (July 2017): 708–15. http://dx.doi.org/10.1139/apnm-2016-0556.
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The cellular stress response of the rat tibialis anterior (TA) muscle was investigated following 20, 40, or 60 lengthening contractions (LCs) using an in vivo model of electrical stimulation. Muscles were removed at 0, 1, 3, or 24 h after LCs and assessed for heat shock transcription factor (HSF) activation, heat shock protein (HSP) content, and/or morphological evidence of muscle fibre damage. When compared with the first muscle contraction, peak muscle torque was reduced by 26% (p < 0.05) after 20 LCs and further reduced to 56% and 60% (p < 0.001) after 40 and 60 LCs, respectively. Following 60 LCs, HSF activation was detected at 0, 1, and 3 h but was undetectable at 24 h. Hsp72 content was elevated at 24 h after 20 LCs (2.34 ± 0.37 fold, p < 0.05), 40 LCs (3.02 ± 0.31 fold, p < 0.01), and 60 LCs (3.37 ± 0.21 fold, p < 0.001). Hsp25 content increased after 40 (2.36 ± 0.24 fold, p < 0.01) and 60 LCs (2.80 ± 0.37 fold, p < 0.01). Morphological assessment of TA morphology revealed that very few fibres were damaged following 20 LCs while multiple sets of LCs (40 and 60) caused greater amounts of fibre damage. Electron microscopy showed disrupted Z-lines and sarcomeres were detectable in some muscles fibres following 20 LCs but were more prevalent and severe in muscles subjected to 40 or 60 LCs. These results suggest LCs elevate HSP content by an HSF-mediated mechanism (60 LC) and a single set of 20 LCs is capable of increasing muscle HSP content without causing significant muscle fibre damage.
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Bakker, Anthony J., Ann L. Parkinson, and Stewart I. Head. "Contractile properties of single-skinned skeletal muscle fibres of the extensor digitorum longus muscle of the Australian short-nosed echidna." Australian Journal of Zoology 53, no. 4 (2005): 237. http://dx.doi.org/10.1071/zo05011.
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Eutherian mammal fast-twitch muscle fibres share similar contractile activation properties, suggesting that these properties are highly conserved in mammals. To investigate this hypothesis, we examined the contractile properties of skeletal muscle from the order Monotremata, a mammalian order that separated from eutherians 150 million years ago. The Ca2+- and Sr2+-activation properties of single mechanically skinned skeletal muscle fibres from the extensor digitorum longus (EDL) muscle of the short-nosed echidna were determined. Sigmoidal curves fitted to force response data plotted as a function of pCa (–log[Ca2+]), had a mean slope of 4.32 ± 0.28 and a mean pCa50 and pCa10 value of 6.18 ± 0.01 and 6.41 ± 0.02 respectively (n = 20). The mean pSr50, pSr10 and slope values of curves fitted to the force-response data after activation with Sr2+ were 4.80 ± 0.03, 5.29 ± 0.07 and 2.75 ± 0.18 respectively (n = 20). The mean pCa50–pSr50 value for the echidna EDL fibres was 1.37 ± 0.04. In five of the echidna fibres, exposure to submaximal Ca2+ concentrations produced myofibrillar force oscillations (mean frequency, 0.13 ± 0.01 Hz), a phenomenon found only in eutherian slow and intermediate muscle fibres. These results show that echidna EDL fibres generally have similar contractile properties to eutherian fast-twitch skeletal muscle fibres, such as those found in the EDL of the rat.
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Brüstle, Berit, Sabine Kreissl, Donald L. Mykles, and Werner Rathmayer. "The neuropeptide proctolin induces phosphorylation of a 30 kDa protein associated with the thin filament in crustacean muscle." Journal of Experimental Biology 204, no. 15 (August 1, 2001): 2627–35. http://dx.doi.org/10.1242/jeb.204.15.2627.
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SUMMARYIn the isopod Idotea emarginata, the neuropeptide proctolin is contained in a single pair of motoneurones located in pereion ganglion 4. The two neurones supply dorsal extensor muscle fibres of all segments. Proctolin (1μmoll−1) potentiates the amplitude of contractures of single extensor muscle fibres elicited by 10mmoll−1 caffeine. In western blots of myofibrillar proteins isolated from single muscle fibres and treated with an anti-phosphoserine antibody, a protein with an apparent molecular mass of 30kDa was consistently found. The phosphorylation of this protein was significantly increased by treating the fibres with proctolin. After separation of myofibrillar filaments, a 30kDa protein was found only in the thin filament fraction. This protein is phosphorylated and detected by an antiserum against crustacean troponin I.
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Coulton, G. R., B. Rogers, P. Strutt, M. J. Skynner, and D. J. Watt. "In situ localisation of single-stranded DNA breaks in nuclei of a subpopulation of cells within regenerating skeletal muscle of the dystrophic mdx mouse." Journal of Cell Science 102, no. 3 (July 1, 1992): 653–62. http://dx.doi.org/10.1242/jcs.102.3.653.
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Degeneration of muscle fibres during the early stages of Duchenne Muscular Dystrophy (DMD) is accompanied by muscle fibre regeneration where cell division and myoblast fusion to form multinucleate myotubes within the lesions appear to recapitulate the events of normal muscle development. The mechanisms that govern the expression of genes regulating differentiation of myoblasts in regenerating skeletal muscle are of great interest for the development of future therapies designed to stimulate muscle regeneration. We show here that single-stranded breaks in DNA are localised in nuclei, using an exogenously applied medium containing labelled deoxynucleotides and the Klenow fragment of DNA polymerase I. The nuclei of a sub-population of cells lying in the inflammatory infiltrate of lesions in the skeletal muscle of the muscular dystrophic mouse (mdx), a genetic homologue of DMD, were labelled in this fashion. By contrast, labelled cells were completely absent from the muscles of normal non-myopathic animals (C57BL/10) and non-lesioned areas of mdx muscles. Cells expressing the muscle-specific regulatory gene, myogenin, were also found within mononucleate cells and myotubes within similar mdx muscle lesions. While we cannot yet say that the cells labelled by the DNA polymerase reaction are in fact differentiating, they were found only in significant numbers within mdx muscle lesions where new muscle fibres appear, providing strong circumstantial evidence that they are intimately associated with the regenerative process. Using a range of nucleases and different DNA polymerases, we show that the DNA polymerase-labelling reaction observed was DNA-dependent and most probably due to infilling of naturally occurring single-stranded gaps in DNA. Since the regenerative process in human Duchenne Muscular Dystrophy is apparently less effective than that seen in mdx mice, continued study of single-stranded DNA breaks may help to elucidate further the mechanisms controlling the expression of genes that characterise the myogenic process during skeletal muscle regeneration. Such findings might be applied in the development of future therapies designed to stimulate muscle regeneration in human dystrophies.
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Heslop, L., J. E. Morgan, and T. A. Partridge. "Evidence for a myogenic stem cell that is exhausted in dystrophic muscle." Journal of Cell Science 113, no. 12 (June 15, 2000): 2299–308. http://dx.doi.org/10.1242/jcs.113.12.2299.
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Injection of the myotoxin notexin, was found to induce regeneration in muscles that had been subjected to 18 Gy of radiation. This finding was unexpected as irradiation doses of this magnitude are known to block regeneration in dystrophic (mdx) mouse muscle. To investigate this phenomenon further we subjected mdx and normal (C57Bl/10) muscle to irradiation and notexin treatment and analysed them in two ways. First by counting the number of newly regenerated myofibres expressing developmental myosin in cryosections of damaged muscles. Second, by isolating single myofibres from treated muscles and counting the number of muscle precursor cells issuing from these over 2 day and 5 day periods. After irradiation neither normal nor dystrophic muscles regenerate to any significant extent. Moreover, single myofibres cultured from such muscles produce very few muscle precursor cells and these undergo little or no proliferation. However, when irradiated normal and mdx muscles were subsequently treated with notexin, regeneration was observed. In addition, some of the single myofibres produced rapidly proliferative muscle precursor cells when cultured. This occurred more frequently, and the myogenic cells proliferated more extensively, with fibres cultured from normal compared with dystrophic muscles. Even after 25 Gy, notexin induced some regeneration but no proliferative myogenic cells remained associated with the muscle fibres. Thus, skeletal muscles contain a number of functionally distinct populations of myogenic cells. Most are radiation sensitive. However, some survive 18 Gy as proliferative myogenic cells that can be evoked by extreme conditions of muscle damage; this population is markedly diminished in muscles of the mdx mouse. A small third population survives 25 Gy and forms muscle but not proliferative myogenic cells.
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Blair, K. L., and P. A. V. Anderson. "Physiological and pharmacological properties of muscle cells isolated from the flatworm Bdelloura candida (Tricladia)." Parasitology 109, no. 3 (September 1994): 325–35. http://dx.doi.org/10.1017/s0031182000078355.
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SummaryA protocol for dissociating single muscle fibres from intact flatworms was developed. Muscle fragments of various sizes were obtained, many with their cell bodies, or myocytons, intact. Many of the fibres were spontaneously contractile, and they and others contracted in response to applications of transmitter candidates, activators of protein kinase C and the anthelmintic praziquantel. The responses were all similar to those evoked in strips of tissue. Voltage clamp recordings from the isolated muscle fibres revealed that they possess an inward Ca2+ current and 3 separate K+ currents. These results indicate that muscle fibres in Bdelloura bear receptors for neurotransmitters and that preparations of dispersed muscle fibres can be used for studying the basic physiological and pharmacological properties of platyhelminth muscle.
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LÄNNERGREN, J., H. WESTERBLAD, and J. D. BRUTON. "Slow recovery of force in single skeletal muscle fibres." Acta Physiologica Scandinavica 156, no. 3 (March 1996): 193–202. http://dx.doi.org/10.1046/j.1365-201x.1996.198000.x.
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LÄNNERGREN, J., and H. WESTERBLAD. "Action potential fatigue in single skeletal muscle fibres ofXenopus." Acta Physiologica Scandinavica 129, no. 3 (March 1987): 311–18. http://dx.doi.org/10.1111/j.1748-1716.1987.tb08074.x.
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De Beer, Evert L., Heather Finkle, Emile E. Voest, Bas G. V. Van Heijst, and Piet Schiereck. "Doxorubicin interacts directly with skinned single skeletal muscle fibres." European Journal of Pharmacology 214, no. 1 (April 1992): 97–100. http://dx.doi.org/10.1016/0014-2999(92)90103-b.
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Maier, L., D. Pette, and W. Rathmayer. "Enzyme activities in single electrophysiologically identified crab muscle fibres." Journal of Physiology 371, no. 1 (February 1, 1986): 191–99. http://dx.doi.org/10.1113/jphysiol.1986.sp015968.
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Rodriguez-Falces, Javier, Luis Gila, and Nonna Alexandrovna Dimitrova. "Evaluation of the criteria to identify single-fibre potentials in human muscle fibres." Biological Cybernetics 106, no. 6-7 (July 18, 2012): 323–38. http://dx.doi.org/10.1007/s00422-012-0500-z.
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EINARSSON, F., T. HULTGREN, B. O. LJUNG, E. RUNESSON, and J. FRIDÉN. "Subscapularis Muscle Mechanics in Children with Obstetric Brachial Plexus Palsy." Journal of Hand Surgery (European Volume) 33, no. 4 (August 2008): 507–12. http://dx.doi.org/10.1177/1753193408090764.
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This study investigates the passive mechanical properties of the subscapularis muscle in children with a contracture as a result of obstetrical brachial plexus palsy. Muscle biopsies were harvested from nine children undergoing open surgery for shoulder contracture. Passive mechanical testing of single cells and muscle bundles was performed. Corresponding comparisons were made using muscle biopsies from seven healthy controls. Single muscle fibres from patients with obstetric brachial plexus palsy displayed a shorter slack sarcomere length, linear deformation of the fibre within a wider zone of sarcomere length and a greater relative increase in stiffness compared with muscle bundles. We conclude that secondary changes in muscle fibre properties will occur as a result of a longstanding lack of sufficient passive stretch, leading to compensatory changes in the extracellular matrix. These results suggest the presence of a dynamic feedback system constituting a muscle-to-extracellular matrix communication interface.
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Allard, Y. E. "Intracellular pH recovery from lactic acidosis of single skeletal muscle fibres." Canadian Journal of Physiology and Pharmacology 66, no. 12 (December 1, 1988): 1560–64. http://dx.doi.org/10.1139/y88-255.
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Intracellular pH (pHi, measured with H+-selective microelectrodes, in quiescent frog sartorius muscle fibres was 7.29 ± 0.09 (n = 13). Frog muscle fibres were superfused with a modified Ringer solution containing 30 mM HEPES buffer, at extracellular pH (pHo) 7.35. Intracellular pH decreased to 6.45 ± 0.14 (n = 13) following replacement of 30 mM NaCl with sodium lactate (30 mM MES, pHo 6.20). Intracellular pH recovery, upon removal of external lactic acid, depended on the buffer concentration of the modified Ringer solution. The measured values of the pHi recovery rates was 0.06 ± 0.01 ΔpHi/min (n = 5) in 3 mM HEPES and was 0.18 ± 0.06 ΔpHi/min (n = 13) in 30 mM HEPES, pHo 7.35. The Na+–H+ exchange inhibitor amiloride (2 mM) slightly reduced pHi recovery rate. The results indicate that the net proton efflux from lactic acidotic frog skeletal muscle is mainly by lactic acid efflux and is limited by the transmembrane pH gradient which, in turn, depends on the extracellular buffer capacity in the diffusion limited space around the muscle fibres.
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Preedy, Victor R., and Timothy J. Peters. "Acute effects of ethanol on protein synthesis in different muscles and muscle protein fractions of the rat." Clinical Science 74, no. 5 (May 1, 1988): 461–66. http://dx.doi.org/10.1042/cs0740461.
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1. The effects of a single dose of ethanol (75 mmol/kg body weight) on rates of muscle protein synthesis were examined in young rats. Fractional rates of protein synthesis were measured in the soleus, plantaris, gastrocnemius, diaphragm and stomach by the large ‘flooding-dose’ technique. 2. After 150 min, the fractional synthesis rates of all muscles were reduced by 15–35%. Skeletal muscles containing a predominance of anaerobic (fast-twitch, type II) fibres showed greater changes when compared with skeletal muscles with a predominance of aerobic (slow-twitch, type I) fibres. 3. Gastrocnemius muscles were separated into sarcoplasmic, stromal and myofibrillar protein fractions. Protein synthesis was reduced similarly in all fractions by ethanol treatment, by approximately 30%. 4. As skeletal muscle mass comprises 40% of body weight, the responses have important physiological implications and may also be responsible for the muscle atrophy observed in alcoholic patients.
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Reed, C. M. "Dye coupling in the muscles controlling squid chromatophore expansion." Journal of Experimental Biology 198, no. 12 (December 1, 1995): 2631–34. http://dx.doi.org/10.1242/jeb.198.12.2631.
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Dye coupling between the cone-shaped radial muscle fibres, which control the expansion and closing of a squid chromatophore organ, was investigated in the squid Loligo vulgaris. Particular attention was paid to the role of the myomuscular junctions located between the muscle fibres. Lucifer Yellow was injected ionophoretically into single muscle fibres under normal artificial sea water (ASW) and under various concentrations of calcium in ASW. Under ASW, 44% of muscle fibres examined were dye-coupled, 82% were coupled under calcium-free sea water and 67% were coupled under sea water containing high concentrations of calcium. Dye transfer was blocked by octanol. Muscle fibres were never seen to link adjacent chromatophore organs. Results are discussed in terms of the role of the myomuscular junctions in the regulation of chromatophore expansion in the living animal.