Hemolytic toxin from the soft coral Sarcophyton trocheliophorum: isolation and physiological characterization

The unifying characteristic of cnidarians is the production of protein and polypeptide toxins. The present study describes the identification of a hemolytic toxin from the soft coral Sarcophyton trocheliophorum. The crude extract was highly cytotoxic (EC50 = 50 ng/mL) against human erythrocytes. It was also tested for hemolytic activity by the blood agar plate method, resulting in a hemolytic halo of 12 mm with 50 µg of protein. The stability of the venom under different physiological conditions was analyzed. The venom hemolytic activity was augmented by alkaline and neutral pH whereas it was reduced in acidic pH. The activity was stable up to 60º C. The hemolytic activity was completely abolished by the addition of serum and reduced significantly during frequent freezing-thawing cycles. Toxin purification was performed by ammonium sulfate precipitation and subsequently desalted by dialysis against 10 mM sodium phosphate buffer (pH 7.2), followed by anion exchange chromatography on DEAE cellulose column and gel filtration chromatography using Sephadex G-50 matrix. The purified active fractions possessed a prominent protein of approximately 45 kDa, as revealed by SDS-PAGE.(AU)

Electrophysiology of the swimming system of hydromedusae and the effects of atropine-induced crumpling

1. In order to evaluate how crumpling behavior influences the swimming system in Liriope tetraphylla, extracellular recordidngs of muscle action potentials related to both behaviors were performed. 2. The swimming pattern of Liriope consists of irregular bursts of muscle potentials. A correlation was obtained between number of muscle potentials and burst lenght and between burst and interburst periods. The swimming pattern could be predicted from the burst length since a long burst was followed by a short period of quiescence and by a burst as long as the preceding one. 3. The addition of atropine to induce radial muscle contraction first caused an increase in swimming activity and then an irreversible reduction. The enhancement of swimming activity was due to the increase of burst length and of the frequency of swimming bursts (due to the decrease of the interburst period), and the reduction of swimming activity, to the enhacement of the intervurst period and to the reduction of the burst length. 4. It is proposed that, when facing a noxious stimulus, Liriope will first "escape" from it by enhancing its swimming activity and, if the stimulus persists, blockade of the pacemaker system becomes accentuated as the radial muscle contractions becomes more sustained