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Comparison of the biological actions of tetrodotoxin and saxitoxin
Abatraets
295
M. H. (Sherrington School of Physiology, St. Thomas's Hospital Medical School, London, England). Black of sensory nerve conduction in the cat by mussel poison and tetrodotoxin. EvANs,
poison and tetrodotoxin black nervous transmission between peripheral nerves and the spinal roots in the cat. Large myelinated sensory fibres become blocked with intravenously administered doses of 4-5-13'îg/ per kg ; large motor fibres were not blocked until the dose was raised by about 30=40 per cent . The conduction block in the sensory fibres first appeared in the region of the dorsal root ganglion, where the safety factor for nervous conduction is lowered by the presence of the collateral branch to the ganglion cell. MUSSES,
KAO, C. Y. (Department Pharmacology, State University of New York, Downstate Medical Center, Brooklyn, New York). Comparison of the biological actions of tetrodotoxin and saxitoxin.
and saxitoxin, although chemically distinct, both act pharmacologically by interfering with the production of action potentials in nerves and skeletal muscle. The intraperitoneal LD in mice is 10 pg per kg body weight . The toxins are active in nanomolar concentrations and thus are 100,000 times more active than local anesthetics such as procaine or cocaine. Their mode of action differs from the latter in that they block only the early increase of ionic permeability associated with sodium influx during excitation. In the neuromuscular system these toxins cause a block in both motor axons and skeletal muscle, while only saxitoxin causes a decrease in the end plate potential Both toxins produce cardiovascular hypotension and present data suggest that this is caused by depression of spinal vasomotor areas or vasomotor nerves rather than by depression of the medullary vasomotor center as previously supposed. In addition, saxitoxin in low doses, as opposed to tetrodotoxin, causes nerve blockage without affecting blood pressure . Respiratory depression is also apparently caused by action outside of thebrain. The autonomic nervous system is resistant, although information concerning saxitoxin is meager . At the cellular level, tetrodotoxin and probably saxitoxin act on the transient molecular arrangements in the excitable membrane to cause the block in nerve impulses. Consequently, a study of the action of. these toxins is important because of their usefulness in studies of excitation phenomena and the molecular structure of excitable membranes. TETRODoToxnv
R. and PECK, M. L. (Department Chemistry, Montana State University, Bozeman, Montana) . The venom of the .honeybee (Apis mell(/era) : I. General character. O'CoNNoR, R., HENDERsoN, G., NEtsoN, D., PARKER,
(Apis nullijera) venom is a complex mixture of carbohydrates, lipids, free amino acids, peptides, proteins and enzymes. Components have been partially characterized and their relative amounts have been partially characterized and their relative amounts have been established. The water content of the venom sac contents has been determined so that the general composition of a honeybee sting may now be estimated. Although individual components often possess interesting biological activity it is doubtful if the physiological properties of the venom can be satisfactorily attributed to single compounds. No single compound, with the possible exception of mellitin, constitutes more than 15 per cent of the dried venom. The venom contains families of similar compounds, such as a number of small peptides, which may result from venom release at a stage of incomplete protein biosynthesis . HONEYBEE
E. and KRAMAR, R. (Department Medical Chemistry, School of Medicine, University . of Vienna, Vienna, Austria) . Biochemistry of the cytotoxic action of amphibian posbihs. KAisER,
Tm: sTRoNG cytotoxic and cytolytic activities of the skin secretions of the yellow-bellied uok B. variegate are not only effective against erythrocytes but also fibroblasts in tissue culture; mast cells in connective tissues, and Ehrlich ascites cells of the mouse. Further, the skin secretions inhibit respii~ntiôn and anaerobic glycolysis of intact tumor cells, and inhibit respiration and phosphorylation of liver"mitochondria. The causes and mechanism responsible for the cytotoxic effects of the skin secretions are presented.
295
M. H. (Sherrington School of Physiology, St. Thomas's Hospital Medical School, London, England). Black of sensory nerve conduction in the cat by mussel poison and tetrodotoxin. EvANs,
poison and tetrodotoxin black nervous transmission between peripheral nerves and the spinal roots in the cat. Large myelinated sensory fibres become blocked with intravenously administered doses of 4-5-13'îg/ per kg ; large motor fibres were not blocked until the dose was raised by about 30=40 per cent . The conduction block in the sensory fibres first appeared in the region of the dorsal root ganglion, where the safety factor for nervous conduction is lowered by the presence of the collateral branch to the ganglion cell. MUSSES,
KAO, C. Y. (Department Pharmacology, State University of New York, Downstate Medical Center, Brooklyn, New York). Comparison of the biological actions of tetrodotoxin and saxitoxin.
and saxitoxin, although chemically distinct, both act pharmacologically by interfering with the production of action potentials in nerves and skeletal muscle. The intraperitoneal LD in mice is 10 pg per kg body weight . The toxins are active in nanomolar concentrations and thus are 100,000 times more active than local anesthetics such as procaine or cocaine. Their mode of action differs from the latter in that they block only the early increase of ionic permeability associated with sodium influx during excitation. In the neuromuscular system these toxins cause a block in both motor axons and skeletal muscle, while only saxitoxin causes a decrease in the end plate potential Both toxins produce cardiovascular hypotension and present data suggest that this is caused by depression of spinal vasomotor areas or vasomotor nerves rather than by depression of the medullary vasomotor center as previously supposed. In addition, saxitoxin in low doses, as opposed to tetrodotoxin, causes nerve blockage without affecting blood pressure . Respiratory depression is also apparently caused by action outside of thebrain. The autonomic nervous system is resistant, although information concerning saxitoxin is meager . At the cellular level, tetrodotoxin and probably saxitoxin act on the transient molecular arrangements in the excitable membrane to cause the block in nerve impulses. Consequently, a study of the action of. these toxins is important because of their usefulness in studies of excitation phenomena and the molecular structure of excitable membranes. TETRODoToxnv
R. and PECK, M. L. (Department Chemistry, Montana State University, Bozeman, Montana) . The venom of the .honeybee (Apis mell(/era) : I. General character. O'CoNNoR, R., HENDERsoN, G., NEtsoN, D., PARKER,
(Apis nullijera) venom is a complex mixture of carbohydrates, lipids, free amino acids, peptides, proteins and enzymes. Components have been partially characterized and their relative amounts have been partially characterized and their relative amounts have been established. The water content of the venom sac contents has been determined so that the general composition of a honeybee sting may now be estimated. Although individual components often possess interesting biological activity it is doubtful if the physiological properties of the venom can be satisfactorily attributed to single compounds. No single compound, with the possible exception of mellitin, constitutes more than 15 per cent of the dried venom. The venom contains families of similar compounds, such as a number of small peptides, which may result from venom release at a stage of incomplete protein biosynthesis . HONEYBEE
E. and KRAMAR, R. (Department Medical Chemistry, School of Medicine, University . of Vienna, Vienna, Austria) . Biochemistry of the cytotoxic action of amphibian posbihs. KAisER,
Tm: sTRoNG cytotoxic and cytolytic activities of the skin secretions of the yellow-bellied uok B. variegate are not only effective against erythrocytes but also fibroblasts in tissue culture; mast cells in connective tissues, and Ehrlich ascites cells of the mouse. Further, the skin secretions inhibit respii~ntiôn and anaerobic glycolysis of intact tumor cells, and inhibit respiration and phosphorylation of liver"mitochondria. The causes and mechanism responsible for the cytotoxic effects of the skin secretions are presented.