Vertebrate slow muscle fibers.

Hess, Arthur

doi:10.1152/physrev.1970.50.1.40

Cited by 278 publications

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“…The voltage dependence of slow fibre m.e.p.c.s was about half that of twitch fibre m.e.p.c.s (also, Dionne & Parsons, 1978), and the spectral shape of current noise from the two cell types was different. Although there are welldocumented electrical (Kuffler & Vaughn-Williams, 1953;Burke & Ginsborg, 1956;Ridge, 1971), biochemical (Lannergren & Smith, 1966, and structural (see Hess, 1970) differences between twitch and slow fibres, this result could not have been anticipated on the basis of the functions of these cells; both twitch and slow fibres are voluntary muscles used in locomotion. The second point to note is the virtual identity of the conductance changes mediated by ACh at end-plates in twitch muscle fibres of amphibians and snakes.…”

Section: Discussionmentioning

confidence: 99%

Characteristics of the acetylcholine‐operated channel at twitch and slow fibre neuromuscular junctions of the garter snake.

Dionne¹,

Parsons²

1981

The Journal of Physiology

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of the slow fibre spectra were not. The latter could be fitted with two Lorentzian components. In all cases the mean end-plate current was proportional to total induced noise variance.4. Two mechanisms which might account for the response differences were identified and tested in a fashion independent of specific molecular kinetics. The different responses do not arise from separate ion-selective channels for the permeant ions at slow fibre end-plates and seem unlikely to derive from separate populations of synaptic and extrasynaptic channels.

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Section: Discussionmentioning

confidence: 99%

Characteristics of the acetylcholine‐operated channel at twitch and slow fibre neuromuscular junctions of the garter snake.

Dionne¹,

Parsons²

1981

The Journal of Physiology

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“…Slow (tonic) skeletal muscle fibres of the frog differ in properties from twitch fibres in several respects (see reviews by Peachey, 1968;Hess, 1970; Costantin, 1975a, b;Linnergren, 1975). These slow fibres are polyneuronally innervated every few millimetres along their length (Kuffler & Vaughan Williams, 1953a;Nasledov, 1965;Nasledov & Thesleff, 1974).…”

Section: Introductionmentioning

confidence: 99%

Mechanical activation in slow and twitch skeletal muscle fibres of the frog.

Gilly¹,

Hui²

1980

The Journal of Physiology

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SUMMARY1. Slow and twitch muscle fibres of the frog were studied with a two-micro-electrode point voltage-clamp method. Slow fibres were identified in pyriformis and cruralis muscles by their appearance in the light microscope, electrical characteristics, and rate of sarcomere shortening or of tension development.2. The relation between the amplitude and duration of threshold depolarizing pulses was determined in sartorius twitch and pyriformis slow fibres. Strengthduration relations for contractile activation are very similar in the two fibre types.3. The effect of a brief subthreshold pulse on the threshold voltage level decays with a half-time of 1-2 msec at 9 0C in both slow and twitch fibres. This fast decay, thought to reflect voltage-dependent deactivation of Ca2+ release following repolarization, is followed by a slower decay of greatly different rates in the two fibre types. The slower components of decay might reflect the rate of background Ca2+ removal by the sarcoplasmic reticulum.4. Reducing external Ca2+ levels to about 01 ftM with 2-5 mM-EGTA has no effect on the shapes of strength-duration curves for both slow and twitch fibres, suggesting that activator Ca2+ in both fibre types originates entirely from intracellular stores.5. 'Tonic' contractions were studied using voltage-clamped short cruralis slow fibres at 20 'C. Reducing external Ca2+ to about 0 1 /LM had no effect on the steepness of the steady-state tension-voltage relation or on the ability of slow fibres to maintain maximal tension during long (200 see) depolarizations to membrane potentials of up to + 50 mV. 6. Functional similarities in activation kinetics of slow and twitch fibres are discussed in relation to the sensing of tubular membrane potential by the sarcoplasmic reticulum, to Ca2+ release from it, and to possible mechanisms involved in these processes. Processes leading to the rapid turning on and off of Ca2+ release in response to changes in tubular membrane potential are probably similar in slow and twitch fibres. However, the apparent lack of voltage-and time-dependent inactivation of Ca2+ release in slow fibre points to a major difference in the two types of muscle.

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“…common in lower vertebrates and birds (Hess, 1970), but do not appear in mammalian locomotory muscles, have been found in the extraocular (Pierobon-Bormioli et al, 1979;Bormioli et al, 1980;Sartore et al, 1987), middle ear (Mascarello et al, 1982), and laryngeal muscles and in the muscle spindles .…”

mentioning

confidence: 99%

Adult human mylohyoid muscle fibers express slow‐tonic, α‐cardiac, and developmental myosin heavy‐chain isoforms

Wang

et al. 2004

Anat. Rec.

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Some adult cranial muscles have been reported to contain unusual myosin heavy-chain (MHC) isoforms (i.e., slow-tonic, ␣-cardiac, embryonic, and neonatal), which exhibit distinct contractile properties. In this study, adult human mylohyoid (MH) muscles obtained from autopsies were investigated to detect the unusual MHC isoforms. For comparison, the biceps brachii and masseter muscles of the same subjects were also examined. Serial cross-sections from the muscles studied were incubated with a panel of isoform-specific anti-MHC monoclonal antibodies that distinguish major and unusual MHC isoforms. On average, the slow type I and fast type II MHC-containing fibers in the MH muscle accounted for 54% and 46% of the fibers, respectively. In contrast to limb and trunk muscles, the adult human MH muscle was characterized by a large proportion of hybrid fibers (85%) and a small percentage of pure fibers (15%; P Ͻ 0.01). Of the fast fiber types, the proportion of the type IIa MHC-containing fibers (92%) was much greater than that of the type IIx MHC-containing fibers (8%; P Ͻ 0.01). Our data demonstrated that the adult human MH fibers expressed the unusual MHC isoforms that were also identified in the masseter, but not in the biceps brachii. These isoforms were demonstrated by immunocytochemistry and confirmed by electrophoretic immunoblotting. Fiber-to-fiber comparisons showed that the unusual MHC isoforms were coexpressed with the major MHC isoforms (i.e., MHCI, IIa, and IIx), thus forming various major/unusual (or m/u) MHC hybrid fiber types. Interestingly, the unusual MHC isoforms were expressed in a fiber type-specific manner. The slow-tonic and ␣-cardiac MHC isoforms were coexpressed predominantly with slow type I MHC isoform, whereas the developmental MHC isoforms (i.e., embryonic and neonatal) coexisted primarily with fast type IIa MHC isoform. There were no MH fibers that expressed exclusively unusual MHC isoforms. Approximately 81% of the slow type I MHC-containing fibers expressed slow-tonic and ␣-cardiac MHC isoforms, whereas 80% of the fast type IIa MHC-containing fibers expressed neonatal MHC isoform. The m/u hybrid fibers (82% of the total fiber population) were found to constitute the predominant fiber types in the adult human MH muscle. At least seven m/u MHC hybrid fiber types were identified in the adult human MH muscle. The most common m/u hybrid fiber types were found to be the MHCI/slow-tonic/␣-cardiac and MHCIIa/neonatal, which accounted for 39% and 33% of the total fiber population, respectively. The multiplicity of MHC isoforms in the adult MH fibers is believed to be related to embryonic origin, innervation pattern, and unique functional requirements.

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Vertebrate slow muscle fibers.

Cited by 278 publications

References 0 publications

Characteristics of the acetylcholine‐operated channel at twitch and slow fibre neuromuscular junctions of the garter snake.

Characteristics of the acetylcholine‐operated channel at twitch and slow fibre neuromuscular junctions of the garter snake.

Mechanical activation in slow and twitch skeletal muscle fibres of the frog.

Adult human mylohyoid muscle fibers express slow‐tonic, α‐cardiac, and developmental myosin heavy‐chain isoforms

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