ABSTRACT
The electric eel Electrophorus electricus is a fresh water teleost showing an electrogenic tissue that produces electric discharges. This electrogenic tissue is distributed in three well-defined electric organs which may be found symmetrically along both sides of the eel. These electric organs develop from muscle and exhibit several biochemical properties and morphological features of the muscle sarcolema. This review examines the contribution of the cytoskeletal meshwork to the maintenance of the polarized organization of the electrocyte, the cell that contains all electric properties of each electric organ. The cytoskeletal filaments display an important role in the establishment and maintenance of the highly specialized membrane model system of the electrocyte. As a muscular tissue, these electric organs expresses actin and desmin. The studies that characterized these cytoskeletal proteins and their implications on the electrophysiology of the electric tissues are revisited.
Subject(s)
Animals , Cytoskeleton/chemistry , Electric Organ/chemistry , Electrophorus/physiology , Actin Cytoskeleton/chemistry , Actin Cytoskeleton/physiology , Actin Cytoskeleton/ultrastructure , Cytoskeleton/metabolism , Cytoskeleton/ultrastructure , Densitometry , Electric Organ/physiology , Electric Organ/ultrastructure , Electrophoresis, Gel, Two-Dimensional , Microscopy, ElectronABSTRACT
1. The electrocytes from the electric organ of the Patagonian ray P. extenta are very unusual cells: semicircular in shape, multinucleated and highly polarized. They have an anterior, concave, innervated face, which exhibits positive histochemical reactions for acetylcholinesterase and for the nicotinic acetylcholine receptor. Multiple nerve-endings are covered with Schwann cell projections, similar to those present in skeletal muscle. Their posterior face is convex, non-innervated and is in contact with collagen fibres. 2. The cytoplasm of these electrocytes possesses abundant filamentous actin (F-actin), orderly distributed in the cell and exhibiting intense fluorescence with NBD-phallacidin. The F-actin is in contact with Z-lines as in muscle, and in contrast with Torpedo (Kordeli et al., 1986, 1987) and Discopyge (Vidal et al., 1986, 1989a) electrocytes, where it is confined to the non-innervated face. 3. Electrocytes of this Rajidae are an ideal model for the study of F-actin because of the similar embryological origin with skeletal muscle tissue and also because of the peculiar characteristics of their cytoplasm, packed full with F-actin. In addition, electric organs could constitute an alternative biological source for the study of the cholinergic synapse.
Subject(s)
Animals , Female , Acetylcholinesterase , Actins , Electric Organ/ultrastructure , Receptors, Nicotinic/metabolism , Skates, Fish , Cytoskeleton , Microscopy, ElectronABSTRACT
Se efectuó un estudio detallado de la ultraestructura del órgano eléctrico de Discopyge tschudii, pez perteneciente al orden Torpediniformes de América del Sur Los resultados describen: a) la citoarquitectura y relaciones topográficas entre los varios tipos de células presentes en este tejido; b) la polarización de los electrocitos, con su región ventral, membrana inervada y membrana dorsal no inervada; c) el espacio intercelular conteniendo axones, células satélites, fibras de colágeno y una lámina basal prominente; d) la sinapsis electromotora: la membrana vental del electrocito muestra evaginaciones e invaginaciones donde se localizan las terminales nerviosas colinérgicas; e) las relaciones entre el electrocito y las células satélites: esta última hace contacto con la zona dorsal del electrocito. Algunas toman las características de macrófagos con pseudópodos lisosomas, y no poseen lámina basal; f) células de Schwann y la formación de la lámina basal. Se postula que una segunda célula de Schwann (SC2) rodea a los axones mielínicos. La evidencia morfológica sugiere que la SC2 secreta y forma la matriz amorfa del espacio extracelular