Reviews 153

CRAWFORD, M. L. J. and SHIBATA, S. (Mississippi Medical Centre, Jackson, Mississippi). Tetrodotoxin and the electrocortical response to light. Br. J. Pharmac. Chemother. 32, 25, 1968.

RATS were immobilized, artifically ventilated, subjected to photic stimulation and the evoked cortical poten- tials recorded. Tetrodotoxin (28 t~g) was injected into the lateral ventricle. Within 5 min, no potentials could be evoked and the electroencephalographic pattern was of low frequency and reduced amplitude. No effect could be obtained after i.p. injection of tetrodotoxin (up to 150 p.g). It is suggested that this inactivity is due to binding at myoneural junctions or to exclusion by a blood-brain barrier. It seems unlikely that this explana- tion is adequate, as others have found depression of cortical excitability after intravenous administration of much smaller doses of tetrodotoxin.

K.R.A.

Tu, A. T. and ADAMS, B. L. (Department of Biochemistry, Colorado State University, Fort Collins, Colorado). Phylogenetic relationships among venomous snakes of the genus

Agkistrodon from Asia and the North American continent. Nature, Lond. 217, 760, 1968.

Antibodies to Agkistrodon rhodostoma were obtained from horses immunized with the venom of Thailand origin and antibodies to A. contortrix laticinctus were prepared from rabbits following immunization. Using the techniques of immunodiffusion and immunoelectrophoresis venoms from A. rhodostoma of Thailand origin and of Malayan origin, A. halys as well as the venoms from the North American specie A. contortrix laticinctus, A. piseivorus piscivorus, and A. bilineatus were tested. A. rhodostoma of Thailand and Malaya are identical on the basis of these tests. A degree of similarity is related to geographical distance. It is con- cluded that in the order of kinship A. halys from Japan lies between A. rhodostoma from S.E. Asia and North American members of Agkistrodon.

W.K.

ASHFORD, A., ROSS, J. W. and SOUTHGATE, P. (Pharmacology Dept., Twyford Laboratories Ltd., London N.W.10). Pharmacology and toxicology of a defibrinating substance from

Malayan pit viper venom. Lancet i, 486, 1968.

A PROTEIN ("arvin") with thrombin-like activity was prepared from venom of Agkistrodon rhodostoma. 1.v. administration of this protein caused the formation of fibrin-like material, and blood incoagulability then resulted from the depletion of plasma fibrinogen and from the formation of anti-thrombin peptides. The effective dosage causing incoagulability showed a remarkable range between species, varying from 0-1 unit per kg in the cat to 90 units per kg in the rat. This was again reflected in the acute toxicity in these species.

Toxicity could be diminished by administering a small dose followed 30-60 min later by a much larger dose, or by slow i.v. administration. Under these conditions, arvin did not appear to affect the circulatory system or respiration, there was no increase in bleeding from stomach ulcers, and no effect on the course of experimental infections or on the activities of centrally-acting drugs. There was some pyrogenic activity in rabbits.

K.R.A.

YASUMOTO, T., NAKAMURA, K. and HASHIMOTO, Y. (Lab. Mar. Biochem., Univ. of Tokyo, Tokyo). A new saponin, Holothurin B, isolated from sea-cucumber, Holothuria vagabunda and

Holothuria lubrica. Agric. biol. Chem. 31, 7, 1967.

THE SEA-CUCUMBER species noted elaborate the same steroidal saponin Holothurin A produced by Actinopyga agassizi, and in addition a second saponin designated as Holothurin B. The newly isolated saponin has been crystallized, and the purified material degraded by acid hydrolysis. From chromatographic analyses of the hydrolysis products, Holothurin B contains as major structuralcomponents a mixture of steroidal aglyconcs (probably the same mixture found in Holothurin A), a half-esterified sulfuric acid moiety, and two sugar residues per molecule (D-quinovose and D-xylose).

S.L.F.