Characterization of desmin in the electric organ of Electrophorus electricus L

The intermediate filament protein of the electric organ from the Electrophorus electricus L. was purified in DEAE-cellulose column after extraction with a Triton X-100 buffer and urea solubilization. The desmin was analysed by SDS-PAGE against desmin purified from chicken gizzard. Characterization of desmin from the electric eel was carried out by peptide mapping and immunoblotting methods.     

Desmin heterogeneity in the main electric organ of Electrophorus electricus

Desmin, the muscle-specific intermediate filament protein was purified from the main electric organ of Electrophorus electricus. It is shown that pure desmin can be separated into 5 isoforms presenting different isoelectric points. These isoforms have similar molecular weight, react with an antibody directed against desmin and generate identical peptides after digestion with protease V8 from Staphylococcus aureus.     

Scanning electron microscopy of the electric organs of Electrophorus electricus L

Summary The surfaces of the organs of Sachs and Hunter of Electrophorus electricus L. were examined by scanning electron microscopy. Special attention was directed to morphological details of the electrocyte to provide a better understanding of its anterior and posterior faces. Some aspects of the microanatomy of these organs, which differ markedly from those of the main electric organ, provide new information on the structure as revealed previously by light and transmission electron microscopy. The relief, mainly expressed by papillae, is related to the actual membrane area, which is important for calculations of specific resistance and conductance. Information is also presented on the general organization of the tissue, in particular the distribution of the connective elements and external configuration of synaptic terminals. Shrinkage in preparation of tissue was evaluated and correction made whenever necessary. Correction factors for actual membrane area were calculated for anterior and posterior faces of electrocytes from both organs.     

Effect of denervation on the glycolytic metabolism of the main electric organ of Electrophorus electricus (L.)

Biochemical modifications of the glycolytic metabolism of the electric organ of Electrophorus electricus (L.) have been studied as a function of denervation. The activities of LDH, MDH and the concentrations of ATP, lactic and pyruvic acids were measured at intervals of zero, 15, 30 and 60 days following denervation. In parallel, CPK activity was also measured. All of these biochemical characteristics were substantially altered by denervation. The results obtained point to a change, after 15 days of denervation, from the normal anaerobic to an aerobic metabolism which remains after 30 days and reverts to anaerobic at 60 days.     

Purification and partial characterization of creatine kinase from electric organ of Electrophorus electricus (L.)

The present investigation deals with the purification and the partial characterization of the soluble creatine kinase (CK) isoenzyme, isolated from the electric organ electrocyte of Electrophorus electricus (L.). Purification was performed by precipitation of the enzyme in the crude extract with ammonium sulfate (80%). The precipitate obtained was analyzed on an ion exchange column of diethylaminoethyl cellulose-52 (DEAE) followed by gel filtration on Superose 12 in a Fast Protein Liquid Chromatography (FPLC) system. Electrophoretic mobility of the active peak confirmed previous results identifying the hybrid isoenzyme MB in the electrocyte cytoplasm. Electrocyte CK is a dimeric enzyme with two identical subunits of approximately 40 kDa as estimated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The sequence analysis of the N-terminal peptide (14 amino acids) of the 40 kDa subunit showed homology with other CK enzymes from electric fish (Torpedo) and human muscle type CK.     

Effect of ATP on purified L(+) lactate dehydrogenase from electric organ of Electrophorus electricus (L.)

L(+) lactate dehydrogenase (LDH) activity from the electric organ of Electrophorus electricus was measured in the presence of ATP in the forward (substrate lactate) and reverse (substrate pyruvate) enzymatic reactions. The I50 for ATP was first determined and then the kinetics of the reactions were investigated with either constant coenzyme (NAD or NADH) concentration and varying substrate (lactate or pyruvate) concentration, or, constant substrate and varying coenzyme concentration. The kinetic data showed that ATP inhibits LDH uncompetitively with respect to the reduced and the oxidized coenzyme. As for the substrates, ATP gives a mixed type inhibition for lactate and a noncompetitive inhibition for pyruvate.     

Observations on the innervated face of the electrocyte of the main organ of the electric eel (Electrophorus electricus L.)

Summary The innervated face of electrocytes in the main electric organ of Electrophorus electricus L. was examined by light microscopy, both conventional and with Nomarski contrast, and by transmission and scanning electron microscopy. Acetylcholinesterase cytochemistry was used in the demonstration of the greater density of synapses over the caudal papillae. The various techniques contributed to a better understanding of the distribution and form of papillae and synapses at the posterior face of the electrocyte. Caudal papillae are longer and thinner than those at the rostral face, but it was not possible to recognize a different type sometimes referred to in the literature as small papillae. The contact of nerve endings with the electrocyte seems to be made predominantly on the terminal half of caudal papillae, however a smaller number occur elsewhere on the posterior face. Synaptic terminals frequently appear as round profiles, but may be also elongated, with or without bulges, usually occupying a depression, and separated from the post-synaptic membrane by a space of 60–100 nm, where an expansion may be found.     

The morphological study of the respiratory organ of Electrophorus electricus

The respiratory organ of Electrophorus electricus is located in the oral cavity and is formed by papillar structures. The papilla consists basically of a cartilaginous central nucleus and is bounded by a connective layer. The results reveal structural adaptations for the respiration among fishes which have efficient respiratory circulation related with the venous blood.