Squid mantle muscle

1981 ◽  
Vol 61 (2) ◽  
pp. 327-342 ◽  
Author(s):  
Q. Bone ◽  
A. Pulsford ◽  
A. D. Chubb
Keyword(s):  
Connective Tissue ◽  
Central Zone ◽  
Circular Muscle ◽  
Fibre Types ◽  
Power Stroke ◽  
Muscle Fibres ◽  
Nerve Terminals ◽  
Vascular Bed

The mantles of the small squid Alloteuthis, the larger Loligo, and the cuttlefish Sepia contain an elaborate framework of connective tissue fibres running in different planes. Some of these fibres are apparently elastic. The circular muscle fibres which provide the power stroke in mantle contraction are of two types. Inner and outer mantle zones consist of well-vascularized mitochondria-rich fibres, whereas the central zone contains only mitochondria-poor fibres with a sparse vascular bed. Nerve terminals on the two fibre types are similar. The radial fibres opposing the circular fibres are of the same type as the central fibres, at least in the mid-region of the mantle. It is suggested that the central fibres are involved in escape jetting contractions, and that the fibres of the inner and outer zones are used during rhythmical respiratory contractions.

On the structure and innervation of the muscle bands of Doliolum (Tunicata: Cyclomyaria)

1974 ◽  
Vol 187 (1088) ◽  
pp. 315-327 ◽  
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Circular Muscle ◽  
Synaptic Cleft ◽  
Muscle Fibres ◽  
Dense Layer ◽  
Nerve Terminals ◽  
20 Nm ◽  
Glycogen Particles ◽  
Electron Lucent ◽  
Myelin Figures

The ultrastructure of the muscle fibres composing the circular muscle bands of Doliolum is described; these muscle fibres are obliquely striated. Each fibre is elongate and multinucleate; peripherally the myofibrillar array borders the fibre, centrally there are long mitochondria with tubular cristae, and vesiculated sarcoplasm containing glycogen particles. Neither a sarcoplasmic reticulum, nor invaginations of the sarcolemma are present; in both gonozooid and oozooid stages myelin figures are frequent in mitochondria and sarcolemma. On atrial and external faces of the fibres there are nerve terminals containing electron-lucent vesicles some 50 nm in diameter. The junctional gap is ca . 10-20 nm wide and is devoid of the dense layer found in the vertebrate synaptic cleft. Each fibre probably receives a number of nerve terminals. The significance of the organization of the muscle fibres is discussed in relation to their role in the locomotion of the animal, and to the structure of other tunicate muscle fibres.

Cholinergic Motor Control of Sea Urchin Tube Feet: Evidence for Chemical Transmission without Synapses

1980 ◽  
Vol 88 (1) ◽  
pp. 281-292
Author(s):  
E. FLOREY ◽  
M. A. CAHILL
Keyword(s):  
Electrical Stimulation ◽  
Connective Tissue ◽  
Outer Surface ◽  
Muscle Fibres ◽  
Nerve Terminals ◽  
Tissue Layer ◽  
Connective Tissue Layer ◽  
Electrical Stimuli ◽  
Tube Feet ◽  
Chemical Transmission

Isolated tube feet of Strongylocentrotus franciscanus contract briefly when the outer epithelium is touched. Similar twitch-like contractions can be induced by electrical stimulation of the outer surface of the tube foot. These responses appear to be chemically mediated. The following evidence indicates that the transmitter substance may be acetylcholine (ACh): ACh causes muscle contraction. This effect and that of electrical stimuli is potentiated by anticholinesterase agents and is antagonized by cholinergic blocking agents. Anaesthesia with chloralhydrate or chloretone abolishes responsiveness to mechanical or electrical stimulation but not to ACh. Desensitization with carbachol prevents responses to ACh and to mechanical or electrical stimulation. There are no neuromuscular synapses and no axons can be detected which cross the connective tissue layer which separates the muscle fibres from the subepithelial nerve plexus. The latter is known to contain conspicuous amounts of ACh; nerve terminals containing clear vesicles invest the outer surface of the connective tissue layer. All evidence indicates that chemical transmission involves diffusion of ACh (released from activated nerve terminals) across this connective tissue layer which is around 5 μm thick in fully extended tube feet but may have a thickness of 20 or even 25 μm in less extended ones. Calculations based on equations describing transmitter diffusion prove the feasibility of such a mechanism. Note:

Distribution of acetylcholine receptors in the vicinity of nerve terminals on skeletal muscle of the frog

1972 ◽  
Vol 181 (1065) ◽  
pp. 431-440 ◽  
Keyword(s):  
Skeletal Muscle ◽  
Connective Tissue ◽  
Neuromuscular Junction ◽  
Muscle Fibre ◽  
Nerve Terminal ◽  
Acetylcholine Receptors ◽  
Postsynaptic Membrane ◽  
Muscle Membrane ◽  
Muscle Fibres ◽  
Nerve Terminals

1. The acetylcholine (ACh) sensitivity of muscle fibres at the neuromuscular junction of the frog was investigated in preparations in which the nerve terminals could be clearly seen. 2. ACh released iontophoretically from a micropipette that was precisely positioned at various points along the muscle fibre in the vicinity of the synapse showed that the peak chemosensitivity (up to 1900 mV/nC) is confined to an area of postsynaptic membrane within a few micra of the nerve terminal; a tenfold decline in sensitivity was obtained when the ACh was released only 5 to 10 μm from the terminal’s edge. It is estimated that most of the response obtained when ACh is released within 40 μm from the terminal (the area covered in this study) is due to diffusion to the immediate postsynaptic area. The extrasynaptic chemosensitivity of the muscle membrane was too low to be measured with the present methods. 3. The accuracy with which micropipettes could be positioned in synaptic areas and the clarity of viewing nerve terminals were improved by bathing the tissue in collagenase, which reduced the amount of connective tissue. The distribution of chemosensitivity remained unchanged by such treatment. The ACh response was not detectably altered when nerve terminals were lifted off the muscle, exposing the subsynaptic muscle surface.

On the respiratory flow in the cuttlefish sepia officinalis.

1994 ◽  
Vol 194 (1) ◽  
pp. 153-165 ◽  
Author(s):  
Q Bone ◽  
E Brown ◽  
G Travers
Keyword(s):  
Connective Tissue ◽  
Circular Muscle ◽  
Mantle Cavity ◽  
Respiratory Pattern ◽  
Muscle Fibres ◽  
Sepia Officinalis ◽  
Cavity Pressure ◽  
Elastic Recoil ◽  
Respiratory Flow ◽  
Large Pressure

The respiratory flow of water over the gills of the cuttlefish Sepia officinalis at rest is produced by the alternate activity of the radial muscles of the mantle and the musculature of the collar flaps; mantle circular muscle fibres are not involved. Inspiration takes place as the radial fibres contract, thinning the mantle and expanding the mantle cavity. The rise in mantle cavity pressure (up to 0.15 kPa), expelling water via the siphon during expiration, is brought about by inward movement of the collar flaps and (probably) mainly by elastic recoil of the mantle connective tissue network 'wound up' by radial fibre contraction during inspiration. Sepia also shows a second respiratory pattern, in which mantle cavity pressures during expiration are greater (up to 0.25 kPa). Here, the mantle circular fibres are involved, as they are during the large pressure transients (up to 10 kPa) seen during escape jetting. Active contraction of the muscles of the collar flaps is seen in all three patterns of expulsion of water from the mantle cavity, electrical activity increasing with increasing mantle cavity pressures. Respiratory expiration in the resting squid Loligo vulgaris is probably driven as in Sepia, whereas in the resting octopus Eledone cirrhosa, the mantle circular musculature is active during expiration. The significance of these observations is discussed.

Cholinergic Innervation of Muscle Fibres in Squid

1982 ◽  
Vol 62 (1) ◽  
pp. 193-199 ◽  
Author(s):  
Q. Bone ◽  
A. Packard ◽  
A. L. Pulsford
Keyword(s):  
Longitudinal Muscle ◽  
Circular Muscle ◽  
Cholinergic Innervation ◽  
Muscle Fibres ◽  
Nerve Terminals ◽  
Thin Sheets ◽  
Excitatory Transmitter ◽  
Radial Muscle ◽  
Electron Lucent ◽  
Longitudinal Fibre

INTRODUCTIONThe small squid Alloteuthis, and the larger Loligo have elongate mantles chiefly made up of two distinct types of circular muscle fibres, partitioned by thin sheets of radial muscle fibres (Bone, Pulsford & Chubb, 1981).Nerve terminals on both types of circular fibre and upon radial fibres contain 50 nm electron-lucent vesicles; preliminary pharmacological investigations (Bone & Howarth, 1980) indicate that L-glutamate is the excitatory transmitter at the terminals upon the circular fibres. In other cephalopods, such as Sepia, and the squids Lepidoteuthis and Taningia (Clarke & Maul, 1962; Clarke, 1967) there are in addition to the circular and radial fibres, layers of longitudinal muscle fibres in the mantle. Such longitudinal fibre layers are lacking over the greater part of the mantle in Alloteuthis and Loligo. In this note, we show that they are present only around the anterior margin of the mantle in these two squid, and that both these anterior longitudinal fibres and the radial fibres of the mantle are insensitive to L-glutamate, but contract in response to acetylcholine, as do the retractor muscles of the head and arms, and the siphon muscles.

The fate of foreign endplates in cross-innervated rat soleus muscle

1980 ◽  
Vol 208 (1171) ◽  
pp. 189-222 ◽  
Keyword(s):  
Muscle Fibre ◽  
Proximal Region ◽  
Presynaptic Terminal ◽  
Motor Axon ◽  
Muscle Fibres ◽  
Nerve Terminals ◽  
Axon Terminals ◽  
Adult Rat ◽  
Rat Soleus Muscle ◽  
Postsynaptic Site

After transplantation of the superficial fibular and the medial plantar nerve to neighbouring sites in the proximal region of adult rat soleus muscles many muscle fibres were initially innervated by axons in both foreign nerves after resection of the original soleus nerve. The foreign endplates were formed at ectopic sites and were often separately locatedon individual muscle fibres. After 3-4 weeks many endplates had been eliminated and most muscle fibres were innervated by only a single foreign axon. Many muscle fibres still had multiple esterase-staining endplate sites in the region innervated by the foreign nerve. On exami­nation by electronmicroscopy, some of these sites were seen to have lost their presynaptic terminal while the postsynaptic structure of the endplate remained intact. Other sites were only partially occupied by motor axon terminals. On each muscle fibre there was always at least one fully occupied endplate region. In some instances separate endplate sites on the same muscle fibre were innervated by branches of the same motor axon. We conclude that the elimination of endplates is due to a competitive interaction between motor axons innervating the same muscle fibre. Morphologically, the elimination of functional endplates is caused by a retraction of nerve terminals from the postsynaptic site.

scholarly journals The effects of temperature and pH on the contractile properties of skinned muscle fibres from the terrapin, Pseudemys scripta elegans

1987 ◽  
Vol 128 (1) ◽  
pp. 87-105 ◽  
Author(s):  
G. Mutungi ◽  
I. A. Johnston
Keyword(s):  
Temperature Dependence ◽  
Dark Field ◽  
Isometric Tension ◽  
Contractile Properties ◽  
Test Method ◽  
Fibre Types ◽  
Muscle Fibres ◽  
Contraction Velocity ◽  
Pseudemys Scripta

Fibre types in the iliofibularis muscle of the freshwater terrapin Pseudemys scripta elegans have been characterized on the basis of their histochemical characteristics, nerve endings and contractile properties. Three types of focally innervated fibres are present, corresponding to the fast glycolytic (Fg), fast oxidative glycolytic (FOG) and slow oxidative (SO) fibre types of other vertebrates. Single fibres or small bundles of fibres representing each histochemical type were identified on the basis of their light scattering properties under dark-field illumination. Fibres were detergent-skinned using Brij 58, and their maximum isometric tension (P0) and unloaded contraction velocity (V0) were determined by the slack test method. At 15 degrees C, fast glycolytic fibres generated maximum isometric tensions of 184 +/− 5 kNm-2 and V0 values of 5.5 +/− 0.3 muscle lengths per second (L0s-1). Slow oxidative fibres produced tensions of 70.6 +/− 3 kNm-2 and had V0 values of 1.3 L0s-1. Tensions and V0 values of fast oxidative glycolytic fibres were between those of Fg and SO fibres. The force-velocity (P-V) characteristics of slow oxidative fibres were studied at 5 degrees and 15 degrees C. Points below 0.6 P0 on the curves could be fitted by a linear form of Hill's equation. Maximum contraction velocities (Vmax) extrapolated from the P-V relationship were 0.62 L0s-1 at 5 degrees C and 0.91 L0s-1 at 15 degrees C. The curvature of the P-V relationship was relatively independent of temperature over the range 5 to 15 degrees C. Values for Hill's constant a/P0 were 0.29 and 0.33 at 5 degrees C and 15 degrees C, respectively. The temperature dependence of P0 and contraction velocity at near zero load (Vi) were studied at constant pH, and under conditions designed to simulate the changes in intracellular pH which occur with temperature in vivo (delta pH/delta T = −0.0186). Changes in pH in the range 6.6 to 7.8 had no effect on either tension or Vi at temperatures between 0 degrees and 20 degrees C. However, below and above this pH range, both tension and Vi were depressed. It is concluded that pH changes within the normal physiological range (6.7-7.8) have no effect on the temperature dependence of P0 and Vi.

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

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.

The Action of the Eyecup Muscles of the Crab, Carcinus, During Optokinetic Movements

1968 ◽  
Vol 49 (2) ◽  
pp. 223-250
Author(s):  
M. BURROWS ◽  
G. A. HORRIDGE
Keyword(s):  
Large Amplitude ◽  
Optokinetic Nystagmus ◽  
Wide Spectrum ◽  
Muscle Tension ◽  
The Other ◽  
Fibre Types ◽  
Muscle Fibres ◽  
Exact Form ◽  
Slow Movement ◽  
The One

1. The actions of the nine eyecup muscles of the crab during horizontal optokinetic movements are described. 2. Each muscle includes a wide spectrum of fibre types, ranging from phasic, with sarcomere lengths of 3-4 µm., through intermediate, to tonic fibres with sarcomeres of 10-12 µm. Each muscle receives at least one slow and one fast motoneuron, but no inhibitory supply. The slow axons predominantly innervate the tonic muscle fibres while the fast axons innervate the phasic ones. 3. Slow movement and the position of the eyecup in space are controlled by the frequency of slow motoneuron discharges. All muscles collaborate at every position. The phasic system is recruited during rapid eyecup movements of large amplitude. 4. In optokinetic nystagmus the exact form of the impulse sequences are described for each muscle. They are the consequence of a visually driven central programme which takes no account of the movement which it generates. Movements in opposite directions involve different central programmes; the one is not merely the reverse of the other. There is no effective proprioceptive feedback from the eyecup joint or from muscle tension receptors.

Isolated Giant Smooth Muscle Fibres in Beroe Ovata: Ionic Dependence of Action Potentials Reveals Two Distinct Types of Fibre

1988 ◽  
Vol 135 (1) ◽  
pp. 343-362 ◽  
Author(s):  
ANDRÉ BILBAUT ◽  
ROBERT W. MEECH ◽  
MARI-LUZ HERNANDEZ-NICAISE
Keyword(s):  
Smooth Muscle ◽  
Action Potential ◽  
Action Potentials ◽  
Marine Invertebrate ◽  
The Body ◽  
Fibre Types ◽  
Resting Membrane Potential ◽  
Muscle Fibres ◽  
Beroe Ovata ◽  
Radial Muscle

1. The ionic dependence of action potentials evoked in giant smooth muscle fibres isolated by enzymatic digestion from the body wall of the marine invertebrate Beroe ovata (Ctenophora) has been investigated using conventional electrophysiological techniques. 2. Differences were observed in the two fibre types studied. The resting membrane potential was −60 ± 1.35 mV (N = 25) in longitudinal muscle fibres and −66 ±1.37 mV (N=32) in radial fibres. Action potentials had a short plateau in longitudinal fibres but not in radial fibres. 3. The action potential overshoot of both fibre types was decreased in Ca2+-free artificial sea water (ASW). In Na+-deficient ASW, action potentials could not be generated in radial fibres and showed a reduced overshoot in longitudinal fibres. 4. Tetrodotoxin (10−5moll−5) added to ASW or Ca2+-free ASW did not affect the action potentials of either type of fibre. 5. Action potentials of both fibres were partially blocked by Co2+ (20–50 mmoll−1) or Cd2+ (l-2mmoll−1). Action potentials of longitudinal fibres in Na+-deficient ASW were abolished by Co2+ (20mmoll−1). In Ca2+-free ASW, the ction potential overshoots of both sets of fibres were restored following the addition of Sr2+ or Ba2+. In longitudinal fibres, Sr2+ increased the duration of the action potential plateau. In both longitudinal and radial muscle fibres, Ba2+ prolonged the action potential. 6. In longitudinal fibres exposed to tetraethylammonium chloride (TEAC1) or 4-aminopyridine (4AP), the action potential was slightly prolonged. In these fibres, TEA+ or 4AP added to Ca2+-free ASW induced only a long-lasting depolarizing plateau. In radial fibres, the action potential duration was slightly increased in the presence of TEA+; it was unaffected by 4AP. In Ca2+-free ASW, TEA+ and 4AP induced an oscillating membrane response which appeared to be dependent on the intensity of the injected current pulse. 7. It is concluded that (a) there are significant differences between the action potentials of longitudinal and radial muscle fibres but that both are dependent on Na+ and Ca2+, (b) in longitudinal fibres, a Ca2+-activated K+ conductance and a TEA+-sensitive voltage-activated K+ conductance contribute to the repolarizing phase of the action potential, the former being predominant, (c) in radial fibres, the repolarizing phase of action potentials probably involves different membrane K+ conductances among which is a TEA+-sensitive K+ conductance.

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