Mutual antagonism between botulinum toxin and -bungarotoxin

Presynaptic neurotoxins with enzymatic activities

Toxins that alter neurotransmitter release from nerve terminals are of considerable scientific and clinical importance. Many advances were recently made in the understanding of their molecular mechanisms of action and use in human therapy. Here, we focus on presynaptic neurotoxins, which are very potent inhibitors of the neurotransmitter release because they are endowed with specific enzymatic activities: (1) clostridial neurotoxins with a metallo-proteolytic activity and (2) snake presynaptic neurotoxins with a phospholipase A2 activity.

Professor Chen-Yuan Lee, MD (1915-2001), pharmacologist: snake venom research at the Institute of Pharmacology, National Taiwan University

Professor Chen-Yuan Lee was born in Tainan, Taiwan. In 1940, he joined the staff of the Institute of Pharmacology of the university, now named National Taiwan University. Dr Lee began a study of Daboia russelli formosensis venom under the direction of Professor Tsungming Tu who, in the 1930s, initiated the pharmacological studies of Formosan snake venoms carried out at the Institute. Under Professor Lee's direction, the Institute became known internationally for its work on the isolation, composition and characterization of the pharmacological properties of neurotoxins isolated from Formosan elapid venoms. Sophisticated use of the latest techniques revealed the mode of action of postsynaptic -bungarotoxin and presynaptic -bungarotoxin from Bungarus multicinctus venom, postsynaptic cobrotoxin, cytotoxic cardiotoxin and phospholipase A2 from Naja naja atra venom. Through work undertaken with colleagues at the Institute and in foreign countries, Professor Lee made an important contribution to our understanding of the mode of action of snake neurotoxins, and to their use in the elucidation of neuromuscular transmission. In the past decade, C.-Y. Lee was a prominent campaigner for social and political justice in Taiwan.

Growth control in primary fetal rat liver cells in culture

Primary fetal rat liver cells cultured in medium deficient in, but not free of, arginine in the presence of dialyzed fetal calf serum grow until the final cell density is attained and cells become quiescent in the Go phase of the cell cycle. When growing cells are transferred into arginine free medium, cells become reversibly arrested in Go. Fetal rat liver cells can be induced to synthesize DNA by addition of high levels of arginine to serum free medium. Low arginine levels in the culture medium do not induce cell growth unless serum is present. Serum stimulates arginine uptake in fetal rat liver cells suggesting that serum growth factor(s) act by increasing intracellular arginine levels high enough to initiate the growth cycle. Fractionation of fetal calf serum by gel filtration on G-200 Sephadex yields a partially purified arginine uptake stimulating activity which is eluted from the column in the same fractions that contain fetal rat liver cell growth promoting activity. Insulin induces DNA synthesis in quiescent fetal rat liver cells. Glucagon reverses the stimulatory effects of insulin. N-6,O-2-Dibutyryl adenosine 3:5-cyclic monophosphoric acid (But2c-AMP) (10-minus4 M) and theophilline (10-minus3 M) inhibit arginine uptake and the initiation of DNA synthesis by serum. The role of arginine in the control of DNA synthesis in fetal rat liver cells and the mechanism of action of serum growth factors are discussed.