Electric organ of fish

In the electric organ of fishes, a number of such stacks are connected in parallel and in series. The total voltage attains 500 V in the electric eel. A current pulse of about 0.5 A develops when this voltage appears across an external circuit (in fresh water or seawater). For the electric ray, these numbers are 60 V and 50 A, respectively. The length of such an electric pulse is comparable with the time of cell membrane excitation (i.e., 1 to 2ms, which is quite sufficient to defeat a designated victim). Some species of fish use pulses repeated at certain intervals. 

The above account is of the nicotinic receptor obtained from the electric organ of fish, but very similar material has been isolated from mammalian skeletal muscle (Dolly and Barnard, 1977 Froehner, Reiness and Hall, 1977). A similar protein, of mol. wt. about 86000, was obtained from the cerebral cortex of the guinea pig. The binding of pHjbungarotoxin to this receptor was inhibited by tubocurarine and gallamine (Bosman, 1972). 

Nicotinic receptors of the vertebrate neuromuscular junction and the electric organs of fishes represent a single subtype, and are known as peripheral receptors. Nicotinic receptors are also found in autonomic ganglia and in the central nervous system, where they are collectively known as neuronal receptors. The latter are also gated cation channels, but structurally they are a heterogeneous group, and less well characterized than peripheral receptors. 

Electrocytes from P, extenta are cup-shaped cells, multinucleated and polarized. They have an anterior, concave, innervated face and a posterior, convex, non-innervated face, that shows a very large system of caveolae (Prado Figueroa et al., 1995). These cup-shaped electrocytes are plesiomorphic, phylogenies based on morphological data (Jacob et al., 1994). Neuronal cell death and synaptic terminal degeneration have been noted in the adult electric organs of fish from the Rajidae family (Fox et al., 1990 and our observations). 

The electric organs of various fish are the richest source of true cholinesterase and yield very pure enzyme preparations by the method of Rothen-... 

Aliens on worlds illuminated by a sun would have vision because of its survival value. On Earth, eyes of various kinds had evolved numerous times in different animal groups. Even certain one-celled organisms have eyelike structures called eyespots. In general, wherever a sense is vital to an animal, there is an accompanying, noticeable accouterment on the body surface. For example, if hearing is vital for an alien, I d expect some form of ear that may be able to swivel in the direction of sound. If the sense of smell is important, we would expect a nose, long proboscis, or forward-projecting snout. On the other hand, if these senses are diminished or unimportant, and an alien relies on a sense like the electrical sense of fish, we would expect the external accouterments to be smaller with less features—eyes, ears, and noses would be smaller. 

Blum, H., J.A. Balschi, and R.G. Johnson, Jr. (1991). Coupled in vivo activity of the membrane band Na+K+ ATPase in resting and stimulated electric organ of the electric fish Narcine brasiliensis. /. Biol. Chem. 266 10254-10259. 

Use of Toxin Binding to Purify a Channel Protein a-Bungarotoxin is a powerful neurotoxin found in the venom of a poisonous snake (Bungarus multicinctus). It binds with high specificity to the nicotinic acetylcholine receptor (AChR) protein and prevents the ion channel from opening. This interaction was used to purify AChR from the electric organ of torpedo fish. 

The nicotinic acetylcholine receptor (NAR) is the most widely studied receptor ion channel. This is due to a very practical reason - availability. The receptor can be isolated in high yield from electric eel or electric ray, both of which use strong electric discharges to incapacitate their prey or for defence. In the electric organs of these fish, the receptor occurs in abimdance in stacks of excitable cells (Figure 9.2). Importantly, however, the NAR and voltage-gated ion channels only occur on one side of the cell. 

Like the acetylcholine receptor channel, the sodium channel also was purified on the basis of its ability to bind a specific neurotoxin. Tetrodotoxin, an organic compound isolated from the puffer fish, binds to sodium channels with great avidity (K nM). The lethal dose of this poison for an adult human being is about 10 ng. The sodium channel was first purified from the electric organ of electric eel, which is a rich source of the protein forming this channel. The isolated protein is a single chain of 260 kd. 

Electric organs of the electric fish have constituted the choice model for studying the nervous cholinergic system (see Changeux, 1981 2010). This chapter shows the autofluorescent chalcedony in electric organs. Autofluorescent chalcedony was also documented in human brains from elderly patients (Prado Figueroa Sanchez Lihon, 2010). 

Viewing things from the perspective of his physical theory of contact electricity, Volta was intrigued by the apparently endless power of the battery to keep the electric fluid in motion without the mechanical actions needed to operate the classical, friction, electrostatic machine, and the electrophorus. He called his batteiy alternately the artificial electric organ, in homage to the torpedo fish that had supplied the idea, and the electromotive apparatus, alluding to the perpetual motion (his words) of the electric fluid achieved by the machine. To explain that motion Volta relied, rather than on the concepts of energy available around 1800, on his own notion of electric tension. He occasionally defined tension as the effort each point of an electrified body makes to get rid of its electricity but above all he confidently and consistently measured it with the electrometer. 

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