Electric ray

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 isolation of the nicotinic acetylcholine receptor glycoprotein was achieved almost simultaneously in several laboratories (those of Changeux, O Brien, Brady, and Eldefrawi) and was helped tremendously by the discovery that the electric organ (elec-troplax) of the electric eel (Electrophorus electricus, an inhabitant of the Amazon River) and related species, as well as the electroplax of the electric ray Torpedo tnar-morata) of the Atlantic Ocean and the Mediterranean Sea, contains acetylcholine receptors (AChR) in a much higher concentration than, for instance, in human neuromuscular endplates or brain tissue. 

Nucleotidase (from Electric ray, Torpedo sp) [9027-73-0]. Purified by dissolving in Triton X-... 

Hughes, G.M. and Johnston, I.A. (1978). Some responses of the electric ray (Torpedo marmorata) to low ambient oxygen tensions. Journal of Experimental Biology 73, 107-117. 

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. 

Page 79, figure 9.3 Journal of Structural Biology, 121 181-190 (1998), Unwin-N The nicotinic acetylcholine receptor of the Torpedo electric ray. Reprinted with permission from Elsevier. 

The torpedo (Torpedo marmorata, also known as the electric ray) has an electric organ, rich in acetylcholine receptors, that can deliver a shock of as much as 200 V for approximately 1 s. [Yves Gladu/Jacana/ Photo Researchers.]... 

The nicotinic receptor has been successfully isolated from the electric ray (Torpedo marmorata) found in the Atlantic Ocean and Mediterranean sea, allowing the receptor to be carefully studied. As a result, a great deal is known about its structure and operation. 

Vogel M, Kowalewski HJ, Zimmermann H, et al. Association of the HNK-1 epitope with 5-nucleotidase from Tomarmorata (electric ray) electric organ. Biochem J. 1991 278 199-202. 

Electric ray. Torpedo sp., 300 Rcqa spp., 26, 715 Thomback ray. Raja clavata, 775 Rudd, Scardinus erythrophthalmus, 147... 

The richest source of nicotinic acetylcholine receptors are the electric organs of the South American electric eel (Electrophorus electricus), the African electric catfish Malapterurus electricus) and the electric ray e.g. the marbled electric ray of the eastern Atlantic Ocean (Torpedo marmoratd) and the Californian electric ray in the northeastern Pacific (Torpedo califomica)) (Fig. 8.36). 

Electric eel (Electrophorus electricus) (left) and marbled electric ray (Torpedo marmorata) (right). 

Evolution has spawn over time a large variety of nicotinic acetylcholine receptor subtypes. The receptor of the electric ray consists of two identical aj-subunits and another three different, pj, y and 6 subunits. The structure of the nicotinic acetylcholine receptor at the neuromuscular endplate is similarly configured. 

Interestingly, the Roman physicians Claudius Galenus (129-199 AD) and Scribonlus Largus (court physician to the Roman emperor Claudius) had already described In their collections of medical recipes (around 47 AD) the use of electric shocks with the Atlantic electric ray Torpedo nobiliana) for the treatment of gout. 

Nucleotidase (from Electric ray, Torpedo sp) [9027-73-0] [EC 3.1.3.5], amorphous. Purify it by dissolving it in Triton X-100 and deoxycholate, and by affinity chromatography on concanavalin A-Sepharose and AMP-Sepharose [Grondal Zimmerman Biochem J 245 805 1987],... 

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