The electromotor system of the electric catfish (Malapterurus electricus): A fine-structural analysis |
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Authors: | A Janetzko Dr H Zimmermann W Volknandt |
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Institution: | (1) Zoologisches Institut der Johann Wolfgang Goethe-Universität, Frankfurt am Main, Federal Republic of Germany;(2) AK Neurochemie, Zoologisches Institut der Johann Wolfgang Goethe-Universität, Siesmayerstr. 70, Postfach 111932, D-6000 Frankfurt 11, Federal Republic of Germany |
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Abstract: | Summary The electromotor system of the electric catfish (Malapterurus electricus) consists of two large ganglion cells situated in the spinal cord, two single axons containing electric nerves and two large electric organs with several million electroplaque cells. The small, irregularly stacked electroplaque cells possess at their center a crater-like indentation from which a stalk like protrusion arises. Many synaptic contacts derived from a single axon collateral are carried on lobe-like protrusions at the terminal knob of this stalk. The electric nerve consists of a large myelinated axon (diameter: 25 m) surrounded by many layers of connective tissue cells. The two ganglion cells (200 m in diameter) are rich in elements of the rough endoplasmic reticulum, Golgi apparatus and lysosomal structures. The cytoplasm of the soma changes its appearance towards the voluminous axon hillock (50 m in diameter) which these organelles do not enter. The cell soma is perforated in a tunnel-like manner by blood capillaries, axons and processes of glial cells. The cell soma and dendrites are covered with two types of synapse. One type forms mixed chemical and electrical (gap junctions) contacts with intermediate attachment plaques. The other type is only chemical in nature. This system may be useful in the study of an identified vertebrate giant neuron. |
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Keywords: | Electric organ Gap junction Synaptic fine structure Giant axon Malapterurus electricus |
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