Electric eel

Harris, W.E. and Stahl, W.L. (1980). Oiganisation of thiol groups of electric eel electric organ Na/K ion stimulated adenosine triphosphatase, studied with bifunctional reagents. Biochem. J. 185, 787-790. 

The availability of purified protein enabled Shosaku Numa and coworkers to clone and sequence the cDNA for the sodium channel from the electroplax cells of the eel electric organ and then from the rat. Subsequently, a large number of sodium channel cDNAs have been cloned from other sources, and sequence comparisons have been made. 

Elucidation of the molecular nature of another cholinergic receptor system, the enzyme acetylcholinesterase. is also being attempted through the use of specific, irreversible inhibitors. Belleau and Tanl have recently demonstrated that N,N-dlmethyl-2-chloro-2 phenylethylamine inactivates erythrocyte acetylcholinesterase when acetylcholine is the substrate.. Other workers have provided evidence that the action of this compound involves alkylation at or near the anionic site of the enzyme, rather then at the esteratlc site. Future studies of this system may well be conducted with pure, crystalline enzyme, if a recent report" of the crystallization of acetylcholinesterase from eel electric tissue can be confirmed. 

Match the sodium (eel electric organ) and potassium (Shaker) channels "with the corresponding properties listed in the right column. 

James, W. M., and Agnew, W. S., 1989, a-(2,8)-polysialic acid immunoreactivity in voltage-sensitive sodium channel of eel electric organ, Proc. R. Soc. London Ser. B 237 233-245. 

The three-dimensional structure of the sodium channel (from electric eel) was determined at 19-A resolution using cryo-electron microscopy and single-particle image analysis. The sodium channel has a bell-shaped outer surface of 135 A in height, 100 A in side length at the square bottom, and 65 A in diameter of the spherical top. An interesting finding is that there are several inner cavities connected to outer orifices. 

In this scheme, EOH is the enzyme, IX is the inhibitor (either a carbamate or an organophosphate). EOH(IX) is analogous to the Michaelis Menton comploc seen with the substrate reaction. EOI is the acyl-enzyme intermediate for carbamates or a phosphoro-enzyme intermediate for the organophosphates. The equilibrium constant for this reaction (K ) is defined as k /k and the phosphorylation or carbamylation constant is defined as k2- In this study 42)y ANTX-A(S) was found to be more specific for AChE than BUChE. The double reciprocal and Dixon plot of the inhibition of electric eel AChE indicated that the toxin is a non-competitive inhibitor decreases, k remains unchanged) (Figure 2). 

In the first group of studies, involving kinetic inhibition studies, comparisons of the uilibrium (K ), phosphorylation (IC), and inhibition constant (K.) for the inhibition of electric eel and human erythrocyte AChE by ANTX-A(S) and DFP were done (Table II). From Table II it is seen that ANTX- A(S) has a higher affinity for human erythrocyte AChE (K =0.253 fiM) than electric eel AChE (K j=3.67 aM). AN DC-A(S) also shows greater affinity for AChE than DFP (K =300 fiM). And finally the bimolecular rate constant, Kj, which indicates the overall rate of reaction, shows AChE is more sensitive toward inhibition by ANTX-A(S) (Kj=1.36 pM- min- ) than DFP (K, = 0.033 /iM- min ). These studies add information to the comparative activity of ANTX-A(S) and other irreversible AChE inhibitors but do not show the site of inhibition. 

Figure 4. Concentration-dependent inhibition of electric eel AChE by ANTX-A(S). AChE and AhTrX-A(S) were incubated for 2 min. before inhibition rate was determined. Key (A) 0.079 ixg/mL ( ) 0.032 xg/mL (V) 0.016 lig/mL >) 0.0032 ig/mL ( ). 0016 tigjmL. NOTE Total inhibition occurs when 0.158 tiglmL ANTX-A(S) is preincubated with AChE for two minutes.

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. 

This was the original hypothesis put forward by Lee (1970) and expanded by Ogilvie et al. (1973). Secretory products of N. brasiliensis do indeed decrease the amplitude of contractions of segments of uninfected rat intestine maintained in an organ bath, but a role for AChE in this phenomenon was discounted due to the heat stability of the parasite factor, and the inability to duplicate the effect with AChE from the electric eel (Foster et al., 1994). Subsequent investigations demonstrated that the suppression of contraction could be duplicated by a 30-50 kDa fraction of secreted products, which contained a protein of 30 kDa that was immunologically cross-reactive with mammalian vasoactive intestinal peptide (VIP). Moreover, an antibody to porcine VIP significantly reduced the inhibitory effect of parasite-secreted products on contraction in vitro (Foster and Lee, 1996). 

Enzyme Commercial acetylcholinesterase preparation - electrical organ acetone powder (extract) from electric eel (Electrophorus electricus) (Sigma, E2384) was used. 

Seto, Y. and T. Shinohara. 1987. Inhibitory effects of paraquat and its related compounds on the acetylcholinesterase activities of human erythrocytes and electric eel (Electrophorus electricus). Agric. Biol. Chem. 51 2131-2138. 

The electric eel (Electrophorus electricus) is a thin fish of length 3-5 feet see Figure 7.19. It is capable of delivering an electric shock of about 600 V as a means... 

Fundamentally, the eel is simply a living battery. The tips of its head and tail represent the poles of the eel s battery . As much as 80 per cent of its body is an electric organ, made up of many thousands of small platelets, which are alternately super-abundant in potassium or sodium ions, in a similar manner to the potentials formed across axon membranes in nerve cells (see p. 339). In effect, the voltage comprises thousands of concentration cells, each cell contributing a potential of about 160 mV. It is probable that the overall eel potential is augmented with junction potentials between the mini-cells. 

A battery is defined as a device for converting chemical energy into electrical energy. A battery is therefore an electrochemical cell that spontaneously produces a current when the two electrodes are connected externally by a conductor. The conductor will be the sea in the example of the eel above, or will more typically be a conductive... 

Cremaschi et al. [39] investigated transepithelial pathways of eel calcitonin, corticotrophin, sucrose, and polyethylene glycol-4000 (PEG-4000) transport across the nasal epithelium using rabbit nasal mucosa mounted on Ussing chamber that was maintained at 27°C. The electrical parameters of the tissues were those of leaky epithelium that allow macromolecules to permeate paracellularly their observation was similar to the finding made by McMartin et al. [40] in which the authors described the nasal epithelium as leaky with... 

E-ct-phenylcinnamic acid, 6 edges, 281 EDX, 168 EDX analyses, 315 EELS, 223 eggshell, 277 eggshell repartition, 257 electrical conductivity, 8 electro-optical properties and quantum confinement,... 

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