Satellite cells of striated muscle after compression injury so slight as not to cause degeneration of the muscle fibres

The linear electrical properties of muscle fibres have been examined using intracellular electrodes for a. c. measurements and analyzing observations on the basis of cable theory. The measurements have covered the frequency range 1 c/s to 10 kc/s. Comparison of the theory for the circular cylindrical fibre with that for the ideal, one-dimensional cable indicates that, under the conditions of the experiments, no serious error would be introduced in the analysis by the geometrical idealization. The impedance locus for frog sartorius and crayfish limb muscle fibres deviates over a wide range of frequencies from that expected for a simple model in which the current path between the inside and the outside of the fibre consists only of a resistance and a capacitance in parallel. A good fit of the experimental results on frog fibres is obtained if the inside-outside admittance is considered to contain, in addition to the parallel elements R m = 3100 Ωcm 2 and C m = 2.6 μF/cm 2 , another path composed of a resistance R e = 330 Ωcm 2 in series with a capacitance C e = 4.1 μF/cm 2 , all referred to unit area of fibre surface. The impedance behaviour of crayfish fibres can be described by a similar model, the corresponding values being R m = 680 Ωcm 2 , C m = 3.9 μF/cm 2 , R e = 35 Ωcm 2 , C e = 17 μF/cm 2 . The response of frog fibres to a step-function current (with the points of voltage recording and current application close together) has been analyzed in terms of the above two-time constant model, and it is shown that neglecting the series resistance would have an appreciable effect on the agreement between theory and experiment only at times less than the halftime of rise of the response. The elements R m and C m are presumed to represent properties of the surface membrane of the fibre. R e and C e are thought to arise not at the surface, but to be indicative of a separate current path from the myoplasm through an intracellular system of channels to the exterior. In the case of crayfish fibres, it is possible that R e (when referred to unit volume) would be a measure of the resistivity of the interior of the channels, and C e the capacitance across the walls of the channels. In the case of frog fibres, it is suggested that the elements R e , C e arise from the properties of adjacent membranes of the triads in the sarcoplasmic reticulum . The possibility is considered that the potential difference across the capacitance C e may control the initiation of contraction.

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Myosin heavy-chain composition in striated muscle after tenotomy

Biochemical Journal ◽

10.1042/bj2820237 ◽

1992 ◽

Vol 282 (1) ◽

pp. 237-242 ◽

Cited By ~ 32

Author(s):

A Jakubiec-Puka ◽

C Catani ◽

U Carraro

Keyword(s):

Myosin Heavy Chain ◽

Heavy Chain ◽

Striated Muscle ◽

Slow Muscle ◽

Fast Muscle ◽

Muscle Fibres ◽

Adult Rats ◽

Tendon Regeneration ◽

Adult Muscle ◽

Gastrocnemius Muscles

The myosin heavy-chain (MHC) isoform pattern was studied by biochemical methods in the slow-twitch (soleus) and fast-twitch (gastrocnemius) muscles of adult rats during atrophy after tenotomy and recovery after tendon regeneration. The tenotomized slow muscle atrophied more than the tenotomized fast muscle. During the 12 days after tenotomy the total MHC content decreased by about 85% in the slow muscle, and only by about 35% in the fast muscle. In the slow muscle the ratio of MHC-1 to MHC-2A(2S) remained almost unchanged, showing that similar diminution of both isoforms occurs. In the fast muscle the MHC-2A/MHC-2B ratio decreased, showing the loss of MHC-2A mainly. After tendon regeneration, the slow muscle recovered earlier than the fast muscle. Full recovery of the muscles was not observed until up to 4 months later. The embryonic MHC, which seems to be expressed in denervated adult muscle fibres, was not detected by immunoblotting in the tenotomized muscles during either atrophy or recovery after tendon regeneration. The influence of tenotomy and denervation on expression of the MHC isoforms is compared. The results show that: (a) MHC-1 and MHC-2A(2S) are very sensitive to tenotomy, whereas MHC-2B is much less sensitive; (b) expression of the embryonic MHC in adult muscle seems to be inhibited by the intact neuromuscular junction.

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Development ofTrichosomoides nasalis(Nematoda: Trichinelloidea) in the murid host: evidence for larval growth in striated muscle fibres

Parasite ◽

10.1051/parasite/2012191019 ◽

2012 ◽

Vol 19 (1) ◽

pp. 19-29

Author(s):

E.H. Fall ◽

M. Diagne ◽

K. Junker ◽

J.M. Duplantier ◽

K. Ba ◽

...

Keyword(s):

Striated Muscle ◽

Larval Growth ◽

Muscle Fibres

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Is the myonuclear domain ceiling hypothesis dead?

Singapore Medical Journal ◽

10.11622/smedj.2021103 ◽

2021 ◽

Author(s):

F Aman ◽

E El Khatib ◽

A AlNeaimi ◽

A Mohamed ◽

AS Almulla ◽

...

Keyword(s):

Satellite Cells ◽

Transcriptional Activity ◽

Muscle Hypertrophy ◽

Muscle Fibres ◽

Adaptation Process ◽

Muscle Adaptation ◽

Upper Limit ◽

Pathological Conditions ◽

Myonuclear Domain ◽

Multinuclear Cells

Muscle fibres are multinuclear cells, and the cytoplasmic territory where a single myonucleus controls transcriptional activity is called the myonuclear domain (MND). MND size shows flexibility during muscle hypertrophy. The MND ceiling hypothesis states that hypertrophy results in the expansion of MND size to an upper limit or MND ceiling, beyond which additional myonuclei via activation of satellite cells are required to support further growth. However, the debate about the MND ceiling hypothesis is far from settled, and various studies show conflicting results about the existence or otherwise of MND ceiling in hypertrophy. The aim of this review is to summarise the literature about the MND ceiling in various settings of hypertrophy and discuss the possible factors contributing to a discrepancy in the literature. We conclude by describing the physiological and clinical significance of the MND ceiling limit in the muscle adaptation process in various physiological and pathological conditions.

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Early thermal experience has different effects on growth and muscle fibre recruitment in spring- and autumn-running Atlantic salmon populations

Journal of Experimental Biology ◽

10.1242/jeb.203.17.2553 ◽

2000 ◽

Vol 203 (17) ◽

pp. 2553-2564 ◽

Cited By ~ 7

Author(s):

I.A. Johnston ◽

H.A. McLay ◽

M. Abercromby ◽

D. Robins

Keyword(s):

Atlantic Salmon ◽

Satellite Cells ◽

Temperature Regime ◽

White Muscle ◽

Growth Patterns ◽

Muscle Fibres ◽

Cross Sectional ◽

Frequency Distributions ◽

Muscle Satellite Cells ◽

First Feeding

The consequence of early thermal experience for subsequent growth patterns was investigated in Atlantic salmon (Salmo salar L.). Spring- and autumn-running salmon were caught in upland (Baddoch) and lowland (Sheeoch) tributaries of the River Dee, Aberdeenshire, Scotland, respectively, on the final stages of their spawning migrations. The eggs were incubated at the simulated natural temperature regime of each stream, which was on average 2.8 degrees C lower for the Baddoch. The offspring, representing 11 families per population, were transferred at first feeding to constant environmental conditions (12–14 degrees C; 16h:8h light:dark photoperiod) and reared in replicate tanks. Salmon of both populations were longer and heavier at 6 and 12 weeks in fish initially reared under the cooler Baddoch regime. Length frequency distributions became bimodal after 18 weeks, and only the upper growth mode was studied. Modelling of length distributions at 40 weeks revealed significantly different patterns of muscle growth according to initial temperature regime, but only for the Sheeoch salmon. In fish of Sheeoch origin, significantly more white muscle fibres were recruited per mm(2) increase in myotomal cross-sectional area at Sheeoch than at Baddoch temperatures (P<0.01). After 40 weeks, the density of white fibres was 10.4 % higher in fish initially reared at the Sheeoch (533+/−6 mm(−2)) than at the Baddoch (483+/−5 mm(−2)) thermal regimes (means +/− s.e.m., 16 fish per group; P<0.001). Muscle satellite cells were identified using an antibody to c-met. At 24 weeks, the density of muscle satellite cells was 29 % higher in Sheeoch salmon reared to first feeding at the temperature of their natal stream than at cooler Baddoch temperatures (P<0.01). In contrast, the number and size distributions of white muscle fibres in the myotomes of Baddoch salmon were independent of early thermal experience.

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The Dogfish Neuromuscular Junction: Dual Innervation of Vertebrate Striated Muscle Fibres?

Journal of Cell Science ◽

10.1242/jcs.10.3.657 ◽

1972 ◽

Vol 10 (3) ◽

pp. 657-665

Author(s):

Q. BONE

Keyword(s):

Neuromuscular Junction ◽

Nerve Terminal ◽

Striated Muscle ◽

Dense Core ◽

The Other ◽

Muscle Fibres ◽

Nerve Terminals ◽

Nerve Fibres ◽

Different Types ◽

Motor End Plate

In the myotomal muscles of the dogfish, Scyliorhinu canicula, there are 2 major types of fibre. The red fibres at the periphery of the myotome receive a distributed en grappe pattern of innervation. There are subjunctional folds at these endings, and the nerve terminals contain vesicles around 50 nm in diameter. In contrast to this, the white twitch fibres of the myotome are innervated focally, by 2 nerve fibres passing to the same motor end-plate. These 2 fibres contain vesicles of different types. One type of nerve terminal contains vesicles around 50 nm in diameter; these terminals resemble those upon the red fibres. The other contains vesicles up to 100 nm in diameter, frequently possessing a dense core. It is suggested that the white twitch fibres of dogfish are innervated by 2 separate axons, possibly containing different transmitter substances.

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