Ultrastructure of intraocular muscles of diving and nondiving ducks

1982 ◽  
Vol 60 (7) ◽  
pp. 1588-1606 ◽  
Author(s):  
J. G. Sivak ◽  
O. E. Vrablic
Keyword(s):  
Neuromuscular Junctions ◽  
Muscle Fibres ◽  
Dark Cell ◽  
Domestic Ducks ◽  
Diving Ducks ◽  
Light Cell ◽  
Axon Terminals ◽  
End Plate ◽  
Transmission Electron ◽  
Skeletal Muscle Fibres

The fine structure of ciliary muscle (CM), iris sphincter (IS), and neuromuscular junctions (NMJ) were studied by light and transmission electron microscopy in domestic ducks (Anas platyrhynchos) and diving ducks (Mergus merganser). Previous work has shown that the iris produces exaggerated acommodative ability in the diver. Both muscles are striated in the two species. While both muscles of domestic ducks and the CM of the diving ducks consist of one cell type, the IS of the latter is made up of two types of cells referred to as "light" and "dark." The "light" cell has long, thin, uniformly distributed mitochondria, while in the "dark" cells they are large, unevenly dispersed and often aggregated subsarcolemmally. The sarcoplasmic reticulum is more abundant in both IS and CM of domestic ducks, while well developed T tubules are seen more regularly in the intraocular muscles of diving ducks.The NMJ's do not show the complexity seen in singly innervated skeletal muscle fibres. All the nerve axon terminals end in a flat shallow trough and postjunctional folds are either nonexistent or very shallow. The NMJ's of the IS of domestic ducks and of the "dark" cell of the IS of diving ducks consist of a large single end plate. That of the CM of domestic ducks consists of a diffuse single end plate while the NMJ of the CM of diving ducks consists of diffuse multiple endings. Nerve endings of similar size and structure but occurring only singly were found on the "light" cell of the IS of domestic ducks.

scholarly journals Presynaptic Proteins as Markers of the Neurotoxic Activity of BmjeTX-I and BmjeTX-II Toxins fromBothrops marajoensis(Marajó Lancehead) Snake Venom

2016 ◽  
Vol 2016 ◽  
pp. 1-10
Author(s):  
Antonio Lisboa ◽  
Rodolfo Melaré ◽  
Junia R. B. Franco ◽  
Carolina V. Bis ◽  
Marta Gracia ◽  
...  
Keyword(s):  
Nerve Terminal ◽  
Neurotransmitter Release ◽  
Acetylcholine Receptors ◽  
Motor Nerve ◽  
Synaptic Proteins ◽  
Muscle Fibres ◽  
Motor Nerve Terminal ◽  
Transmission Electron ◽  
Skeletal Muscle Fibres

Neuromuscular preparations exposed toB. marajoensisvenom show increases in the frequency of miniature end-plate potentials and twitch tension facilitation followed by presynaptic neuromuscular paralysis, without evidences of muscle damage. Considering that presynaptic toxins interfere into the machinery involved in neurotransmitter release (synaptophysin, synaptobrevin, and SNAP25 proteins), the main objective of this communication is to analyze, by immunofluorescence and western blotting, the expression of the synaptic proteins, synaptophysin, synaptobrevin, and SNAP25 and by myography, light, and transmission electron microscopy the pathology of motor nerve terminals and skeletal muscle fibres of chick biventer cervicis preparations (CBC) exposedin vitroto BmjeTX-I and BmjeTX-II toxins fromB. marajoensisvenom. CBC incubated with toxins showed irreversible twitch tension blockade and unaffected KCl- and ACh-evoked contractures, and the positive colabelling of acetylcholine receptors confirmed that their action was primarily at the motor nerve terminal. Hypercontraction and loose myofilaments and synaptic vesicle depletion and motor nerve damage indicated that the toxins displayed both myotoxic and neurotoxic effect. The blockade resulted from interference on synaptophysin, synaptobrevin, and SNAP25 proteins leading to the conclusion that BmjeTX-I and BmjeTX-II affected neurotransmitter release machinery by preventing the docking of synaptic vesicles to the axolemma of the nerve terminal.

Electrophysiology and electron-microscopy of rat neuromuscular junctions after nerve degeneration

1968 ◽  
Vol 169 (1016) ◽  
pp. 289-306 ◽  
Keyword(s):  
Electron Microscopy ◽  
Schwann Cell ◽  
Neuromuscular Junction ◽  
Neuromuscular Junctions ◽  
Diaphragm Muscle ◽  
Nerve Degeneration ◽  
Muscle Membrane ◽  
Muscle Fibres ◽  
Denervated Muscle ◽  
End Plate

(1) Intracellular micro-electrodes and electron-microscopy were used to study normal and denervated end-plates in rat diaphragm muscle fibres. (2) In normal muscles 84.5 to 100% of the micro-electrode insertions were sufficiently close to the neuromuscular junction to detect miniature end-plate potentials. The structure of the normal neuromuscular junction had the usual 3-cell arrangement: muscle with synaptic folds, axon and Schwann cell. (3) Within one day after section of the phrenic nerve, the axon disintegrated and miniature end-plate potentials ceased to occur. Subsequently, miniature potentials were not observed at denervated end-plates, except during the third week after denervation, at which time a low-frequency discharge was seen in eight out of 770 fibres. The miniature potentials at these end-plates resembled those at normal junctions, and were presumably also due to acetylcholine acting on the muscle membrane. (4) The synaptic folds remain for several months after denervation, and serve to identify electron-microscopically the denervated end-plate. After prolonged denervation (> 3 weeks), when miniature end-plate potentials were never observed, there was generally no cell overlying the synaptic folds. (5) During the first 3 weeks after denervation, a nucleated cell, presumably the Schwann cell, was in close contact with the muscle. ‘Schwann-muscle' contacts were observed in muscle without miniature end-plate potentials. (6) Electron microscopy of a portion of denervated muscle, which included a fibre with miniature potentials, showed that the fibre had extensive ‘Schwann-muscle’ contacts. (7) It is concluded that the Schwann cell is the source of the packages of acetylcholine which evoke miniature end-plate potentials in denervated muscle. Since the Schwann cell was in contact with muscle fibres without miniature potentials, it appears that the presence of the Schwann cell is a necessary, but not a sufficient, condition for the production of miniature potentials at denervated end-plates.

scholarly journals DEVELOPMENT OF THE NEUROMUSCULAR JUNCTION

1972 ◽  
Vol 55 (1) ◽  
pp. 93-103 ◽  
Author(s):  
Thomas L. Lentz
Keyword(s):  
Schwann Cell ◽  
Cholinesterase Activity ◽  
Neuromuscular Junctions ◽  
Synaptic Cleft ◽  
Axon Terminals ◽  
End Plate ◽  
Motor End Plate ◽  
Motor End Plates

To determine the effects of nerve explants on the integrity of motor end plates in vitro, cholinesterase activity and structure of end plates were compared in newt muscle denervated in vivo, cultured in the absence of nerve explants, and cultured in the presence of sensory ganglia. In neuromuscular junctions denervated in vivo or in vitro, the synaptic vesicles become clumped and fragmented. A few intact vesicles escape into the synaptic cleft. Axon terminals degenerate until they are left as residual bodies within the Schwann cell cytoplasm. Junctional folds on the muscle surface are reduced in height and are no longer evident once traces of axoplasm within the Schwann cell disappear. End plate cholinesterase activity is reduced as junctional folds are lost. When muscle is cultured in the presence of a sensory ganglion, the terminal axoplasm degenerates in the same manner but junctional folds persist on the muscle surface. Moderately intense cholinesterase activity remains in association with the junctional folds, so that normal motor end plates are maintained in the absence of innervation. These results show that degenerative changes in the structure of the motor end plate and loss of cholinesterase activity occurring in organ culture as a result of denervation can be retarded by nerve explants that do not directly innervate the muscle.

Morphological and physiological changes in dissociated adult frog muscle fibres after prolonged culturing

1983 ◽  
Vol 219 (1214) ◽  
pp. 91-101 ◽  
Keyword(s):  
Action Potentials ◽  
Striated Muscle ◽  
Neuromuscular Junctions ◽  
Rana Temporaria ◽  
Muscle Fibres ◽  
Adult Frog ◽  
Electron Microscopical ◽  
Skeletal Muscle Fibres ◽  
Miniature Endplate Potentials

Adult frog ( Rana temporaria ) muscle fibres, denervated in vivo , were dissociated and maintained in culture for several weeks. Light and electron microscopical studies showed that the fibres developed striated muscle sprouts. These sprouts were in cytoplasmic continuity with the parent muscle fibre. To judge by the presence of miniature endplate potentials, embryonic Xenopus laevis neurons were able to form functional neuromuscular junctions, both on the muscle sprouts and on the parent fibre. In addition to the usual depolarizing action potentials, the cultured fibres, with or without sprouts, showed slow hyperpolarizing regenerative responses. These hyperpolarizing action potentials were triggered when the membrane potential reached about –120 mV and their ‘peak’ amplitude was at about –230 mV. It is concluded that new skeletal muscle fibres can be formed from outgrowths of adult muscle fibres, and that these sprouts can accept motor innervation.

The ultrastructure of the epidermis of the redia and cercaria of Parorchis acanthus, Nicoll. A study by scanning and transmission electron-microscopy

Parasitology ◽  
1971 ◽  
Vol 62 (3) ◽  
pp. 479-488 ◽  
Author(s):  
Gwendolen Rees
Keyword(s):  
Electron Micrographs ◽  
Technical Assistance ◽  
Ventral Surface ◽  
The Body ◽  
Muscle Fibres ◽  
Scanning Electron Micrographs ◽  
Large Area ◽  
Transmission Electron ◽  
Parorchis Acanthus ◽  
Scanning Electron

Scanning electron-micrographs have shown the covering of microvilli on the surface of the redia of Parorchis acanthus. In the contracted state the elongated microvilli with bulbous extremities seen in the surface grooves may be the result of compression. The surface of the epidermis of the cercaria is smooth on a large area of the ventral surface and lattice-like with microvilli, laterally, anteriorly, dorsally and on the tail. The spines on the body can be withdrawn into sheaths by the contraction of muscle fibres inserted into the basement lamina below each spine.I would like to express my sincere gratitude to Dr I. ap Gwynn of this department for preparing the scanning electron-micrographs and the School of Engineering Science, University of North Wales, Bangor for the use of their stereoscan. I should also like to thank Mr M. C. Bibby for technical assistance and Professor E. G. Gray and Dr W. Sinclair for assistance with the transmission electron-micrographs.

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