- Email: [email protected]
Effect of Gymnodinium breve toxin on frog striated muscle
532
INTERNATIONAL SOC. OF TOXINOLOGY, 1972 GENERAL MEETING It was concluded that the veratridine depolarization is due primarily to an increase in resting membrane permeability to sodium ions. Cevadine (104M) exerted similar effects but was less potent than veratridine in depolarizing the membrane and more potent in increasing negative after-potential andinitiating repetitive discharges. Protoveratrine AandB depolarized the membrane and suppressed the action potential only slightly, but augmented the negative after-potential. Veratramine, isorubijervine, muldamine, and de-esterified parent of muldamine were effective in blocking the action potential with negligible depolarization . Voltage clampexperiments revealed that de-esterified muldaminesuppressed both sodium andpotassium conductance increases. However, cyclopamine, jervine, rubjjervine, and veratrosine had no effect on the resting and action potentials. Sparteine did not affect the resting potential, but had a profound effect on the action potential, its falling phase being greatly prolonged forming a plateau phase. This effect was due to a suppression of the potassium conductance increase . The sodium conductance increase was only negligibly suppressed, and the sodium inactivation was not affected . Thus it can be said that slight modifications of the chemical structure of veratrum alkaloids could drastically change their mode of action . Sparteine is unique in its selective blocking action on the potassium conductance . (Supported by NIH grant NS03437) .
G. M. PADILLA and D. F. MARTIN. (Department of Physiology and Pharmacology, Duke University Medical Center, Durham, N.C . ; Department of Chemistry, University of South Florida, Tampa, Fla.) . Interaction of prymnesium parvwn toxin with red cell membrane . Rates of hemolysis of rabbit erythrocyte suspensions induced by Prymnesium parvum (prymnesin) have been measured colorimetrically at 25° and pH 5-5. The data have been treated as consecutive first-order rate processes associated with the prolytic and lytic periods from which two specific rate constants have been obtained, k' and k, respectively . These are correlated with the binding properties, interaction with exogenous lipids, and cell-volume population changes, and response to membrane modifying drugs. This research was supported in part by Grant 2 R01 FD-00120-0 from the Food and Drug Administration. Z. PAsTER . (Department of Zoology, Tel Aviv University, Israel). Effect of Gynwwdinium breve toxin on frog striated muscle . The direct effect of purified Gymnodinium breve toxin on frog sartorious muscle was investigated. The toxin evokes muscle fibrillation without producing any recorded tension. This fibrillation was a result of a synchronous contraction of single fibers. The fiber's contraction was attributed to spontaneous electrical activity of thefiber, induced by the presence of G. breve toxin. The toxic effect can be blocked by increasing the Ca'+ concentration in the bathing solution, while lowering the Ca2 + concentration caused the muscle to be very sensitive to G. breve toxin. A mechanism is proposed . B. PER= and T. A. FREYVOGEL. (Swiss Tropical Institute, Basel, Switzerland) . Further investigations on the venom of the East African orthognath spider, Pterinochilus spec . The yield of fresh venom can be increased by electric stimulation of the spiders' chelicerae (9 volts d.c .) and by more frequent 'milkings' (at 14 days' intervals) . The average yield is approximately 15 mg of fresh venom per animal . The LDsu of fresh venom for white mice (NMRI) is about 2 l+g per g body weight by the intravenous route. Three different methods are applied to separate and purify the crude venom: gel filtration on Sephadex G-50 fine, acrylamide electrophoresis and isoelectric focusing. So far, it has been found that 2-3 components of the 15-20 substances (mol. wt . > 1400) of the crude venom are toxic for mice. The three toxic constituents seem to be of polypeptide nature, with a molecular weight of about 7000 . No differences could be observed between the venom of males and females, neither with respect to venomyield, nor to toxicity andcomposition . Experiments to improve the separation of the substances concernedareunder way. Toxicity tests on mice and invertebrates will follow . 7017CON 1972 Vol. 10.
INTERNATIONAL SOC. OF TOXINOLOGY, 1972 GENERAL MEETING It was concluded that the veratridine depolarization is due primarily to an increase in resting membrane permeability to sodium ions. Cevadine (104M) exerted similar effects but was less potent than veratridine in depolarizing the membrane and more potent in increasing negative after-potential andinitiating repetitive discharges. Protoveratrine AandB depolarized the membrane and suppressed the action potential only slightly, but augmented the negative after-potential. Veratramine, isorubijervine, muldamine, and de-esterified parent of muldamine were effective in blocking the action potential with negligible depolarization . Voltage clampexperiments revealed that de-esterified muldaminesuppressed both sodium andpotassium conductance increases. However, cyclopamine, jervine, rubjjervine, and veratrosine had no effect on the resting and action potentials. Sparteine did not affect the resting potential, but had a profound effect on the action potential, its falling phase being greatly prolonged forming a plateau phase. This effect was due to a suppression of the potassium conductance increase . The sodium conductance increase was only negligibly suppressed, and the sodium inactivation was not affected . Thus it can be said that slight modifications of the chemical structure of veratrum alkaloids could drastically change their mode of action . Sparteine is unique in its selective blocking action on the potassium conductance . (Supported by NIH grant NS03437) .
G. M. PADILLA and D. F. MARTIN. (Department of Physiology and Pharmacology, Duke University Medical Center, Durham, N.C . ; Department of Chemistry, University of South Florida, Tampa, Fla.) . Interaction of prymnesium parvwn toxin with red cell membrane . Rates of hemolysis of rabbit erythrocyte suspensions induced by Prymnesium parvum (prymnesin) have been measured colorimetrically at 25° and pH 5-5. The data have been treated as consecutive first-order rate processes associated with the prolytic and lytic periods from which two specific rate constants have been obtained, k' and k, respectively . These are correlated with the binding properties, interaction with exogenous lipids, and cell-volume population changes, and response to membrane modifying drugs. This research was supported in part by Grant 2 R01 FD-00120-0 from the Food and Drug Administration. Z. PAsTER . (Department of Zoology, Tel Aviv University, Israel). Effect of Gynwwdinium breve toxin on frog striated muscle . The direct effect of purified Gymnodinium breve toxin on frog sartorious muscle was investigated. The toxin evokes muscle fibrillation without producing any recorded tension. This fibrillation was a result of a synchronous contraction of single fibers. The fiber's contraction was attributed to spontaneous electrical activity of thefiber, induced by the presence of G. breve toxin. The toxic effect can be blocked by increasing the Ca'+ concentration in the bathing solution, while lowering the Ca2 + concentration caused the muscle to be very sensitive to G. breve toxin. A mechanism is proposed . B. PER= and T. A. FREYVOGEL. (Swiss Tropical Institute, Basel, Switzerland) . Further investigations on the venom of the East African orthognath spider, Pterinochilus spec . The yield of fresh venom can be increased by electric stimulation of the spiders' chelicerae (9 volts d.c .) and by more frequent 'milkings' (at 14 days' intervals) . The average yield is approximately 15 mg of fresh venom per animal . The LDsu of fresh venom for white mice (NMRI) is about 2 l+g per g body weight by the intravenous route. Three different methods are applied to separate and purify the crude venom: gel filtration on Sephadex G-50 fine, acrylamide electrophoresis and isoelectric focusing. So far, it has been found that 2-3 components of the 15-20 substances (mol. wt . > 1400) of the crude venom are toxic for mice. The three toxic constituents seem to be of polypeptide nature, with a molecular weight of about 7000 . No differences could be observed between the venom of males and females, neither with respect to venomyield, nor to toxicity andcomposition . Experiments to improve the separation of the substances concernedareunder way. Toxicity tests on mice and invertebrates will follow . 7017CON 1972 Vol. 10.