The contractile properties of slow muscle fibres in sheep extraocular muscle.

Browne, J. S. L.

doi:10.1113/jphysiol.1976.sp011245

Cited by 35 publications

(17 citation statements)

References 25 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…First, in the present study the type of innervation of the fibres was identified directly by the features of the synaptic activity while the mentioned authors based their identification on other criteria. As held by Pilar (1967), Barmack, Bell & Rence (1971) and Browne (1976) it is possible that these criteria were not specific for the recognition of multiple innervation. Secondly, it is conceivable that the cellular population of the muscle regions explored in the above-mentioned studies and in the present analysis were different.…”

Section: Electrical Properties Of Extraocular Musclesmentioning

confidence: 99%

“…Bach-y-Rita & Ito (1966) and Lennerstrand (1974) have reported that in cat extraocular muscles a large number of fibres are multiply innervated and have action potentials. The existence of such fibre type has been questioned on the basis that the criteria used for their identification were not specific enough (Pilar, 1967;Barmack, Bell & Rence, 1971;Browne, 1976). Nevertheless, a very small number of fibres that are multiply innervated and capable of firing action potentials has been identified electrophysiologically in cat (Hess & Pilar, 1963) and in rabbit extraocular muscles, in a combined histological and electrophysiological study (Ozawa, Cheng, Davidowitz & Breinin, 1969).…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Electrophysiological identification of two types of fibres in rat extraocular muscles.

Chiarandini¹,

Stefani²

1979

The Journal of Physiology

View full text Add to dashboard Cite

SUMMARY1. The synaptic potentials and electrical properties of rat inferior rectus muscles were examined in vitro.2. In most fibres the spontaneous synaptic activity consisted of typical miniature end-plate potentials which had a normal distribution of amplitudes and rather uniform time courses. Suprathreshold and maximal nerve stimulation evoked unitary end-plate potentials (e.p.p.s). The synaptic activity of these fibres could be recorded only in the innervation zone of the muscle. These fibres were identified as being focally innervated.3. Focally innervated fibres gave action potentials upon direct and indirect stimulation. They had an effective resistance (Reff) of 1'62 + 022 MQ (mean + S.E., twenty-two fibres) and a time constant (Tm) of 3-8 + 04 msec (twenty-one fibres).Voltage-current curves in control saline were linear between membrane potentials of -50 to -140mV. 4. In a small number of fibres the spontaneous synaptic activity consisted of miniature small-nerve junction potentials which had a skewed distribution of amplitudes with predominance of smaller voltages and time courses with a wide range of variation. Nerve stimulation evoked composite small-nerve junction potentials (s.j.p.s) which could be resolved into unitary components by varying the strength of stimulation. S.j.p.s had a higher threshold than e.p.p.s. Synaptic potentials could be recorded outside the innervation zone, at various sites along the muscle length. These fibres were recognized as being multiply innervated with polyneuronal innervation.5. Multiply innervated fibres lacked action potentials, had a large Reff of 6-0 + 1-1 MD (six fibres) and a prolonged Tm of 29-8 + 4*8 msec. Reff show a moderate decrease to hyperpolarization and a rather large decrease to depolarization which denote, respectively, the presence of anomalous and delayed rectification.6. It is concluded that rat extraocular muscles contain at least two populations of muscle fibres that in terms of synaptic activity and electrical properties are comparable to twitch fibres of other mammalian muscles and to slow or tonic fibres of amphibians.

show abstract

Section: Electrical Properties Of Extraocular Musclesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Electrophysiological identification of two types of fibres in rat extraocular muscles.

Chiarandini¹,

Stefani²

1979

The Journal of Physiology

View full text Add to dashboard Cite

show abstract

“…They have a much slower rise in tension to tetanic nerve stimulation than twitch fibers, are very resistant to fatigue, and are suited to maintaining tension over long periods (Browne, 1976;Lennerstrand and Nichols, 1977;Morgan and Proske, 1984;Nelson et al, 1986). On the basis of these properties, the nontwitch muscle fibers would be suited to a tonic function in eye muscle control.…”

mentioning

confidence: 96%

Twitch and nontwitch motoneuron subgroups in the oculomotor nucleus of monkeys receive different afferent projections

Wasicky

Horn

Büttner‐Ennever

2004

J of Comparative Neurology

View full text Add to dashboard Cite

Motoneurons in the primate oculomotor nucleus can be divided into two categories, those supplying twitch muscle fibers and those supplying nontwitch muscle fibers. Recent studies have shown that twitch motoneurons lie within the classical oculomotor nucleus (nIII), and nontwitch motoneurons lie around the borders. Nontwitch motoneurons of medial and inferior rectus are in the C group dorsomedial to nIII, whereas those of inferior oblique and superior rectus lie near the midline are in the S group. In this anatomical study, afferents to the twitch and nontwitch subgroups of nIII have been anterogradely labeled by injections of tritiated leucine into three areas and compared. 1) Abducens nucleus injections gave rise to silver grain deposits over all medial rectus subgroups, both twitch and nontwitch. 2) Laterally placed vestibular complex injections that included the central superior vestibular nucleus labeled projections only in twitch motoneuron subgroups. However, injections into the parvocellular medial vestibular nucleus (mvp), or Y group, resulted in labeled terminals over both twitch and nontwitch motoneurons. 3) Pretectal injections that included the nucleus of the optic tract (NOT), and the olivary pretectal nucleus (OLN), labeled terminals only over nontwitch motoneurons, in the contralateral C group and in the S group. Our study demonstrates that twitch and nontwitch motoneuron subgroups do not receive identical afferent inputs. They can be controlled either in parallel, or independently, suggesting that they have basically different functions. We propose that twitch motoneurons primarily drive eye movements and nontwitch motoneurons the tonic muscle activity, as in gaze holding and vergence, possibly involving a proprioceptive feedback system.

show abstract

“…Physiological studies in cats demonstrate that the EOM fibers with a multiterminal innervation do not propagate action potentials (Lennerstrand, 1975;Lennerstrand and Nichols, 1977) and are similar to other slow fibers found in birds and amphibians (Morgan and Proske, 1984). Due to their relative inaccessibility, the role of these fibers in the generation of ocular movements is poorly understood although it has been suggested that they serve to smooth and dampen the action of antagonistic muscles (Browne, 1976).…”

Section: Global Zone Fibersmentioning

confidence: 97%

Mitochondrial morphometrics of histochemically identified human extraocular muscle fibers

1986

View full text Add to dashboard Cite

Three fiber types--coarse, granular, and fine--were readily identified in histochemical cryostat sections of human extraocular muscle (EOM). The cryostat retrieval method was utilized to identify these three fiber types in serial electron microscopic thin sections. Using morphometric techniques, five mitochondrial variables (mitochondrial volume fraction, mitochondrial profile size, mitochondrial profile density, and clusters of two or of three or more mitochondrial profiles) were determined for a total of 162 histochemically identified fibers from two regions (orbital and global zones) from six EOMs. Coarse fibers had numerous large-sized mitochondrial profiles, often occurring in clusters. Granular fibers had fewer and smaller-sized profiles scattered across the fiber. Fine fibers had the most numerous, but smallest-sized mitochondrial profiles. Despite significant differences in group (fiber types) means for the mitochondrial variables, no single variable was sufficient for separating fiber types into distinct populations. Although a scattergram plot of two variables was sufficient to separate orbital zone fibers, a computer-generated, multivariate discriminant analysis was needed to separate the global zone fibers into distinct populations. These results will aid future studies on normal and pathological human EOM by providing a morphometric basis for identifying fiber types in the orbital and global zones.

show abstract

The contractile properties of slow muscle fibres in sheep extraocular muscle.

Cited by 35 publications

References 25 publications

Electrophysiological identification of two types of fibres in rat extraocular muscles.

Electrophysiological identification of two types of fibres in rat extraocular muscles.

Twitch and nontwitch motoneuron subgroups in the oculomotor nucleus of monkeys receive different afferent projections

Mitochondrial morphometrics of histochemically identified human extraocular muscle fibers

Contact Info

Product

Resources

About