Abstract: Azatoxin and derivatives thereof are illustrative of a new class of antitumor drugs that are topoisomerase II (top 2) inhibitors. The pharmacophore inhibits the catalytic activity of the purified enzyme but does not unwind relaxed or supercoiled DNA. It is nonintercalative and has at least two domains: a quasiplanar polycyclic ring system, which may bind between DNA base pairs, and a pendant substituent thought to interact with the enzyme, with the DNA grooves or with both. In SV40 and c-myc DNA, azatoxin induces numerous double-strand breaks according to a cleavage pattern which differs from those of known top 2 inhibitors. Azatoxin also is a potent inhibitor of tubulin polymerization.

Abstract: 2-Keto-L-gulonic acid is separated from a fermented medium containing the calcium salt of 2-keto-L-gulonic acid, by carrying out the following operations: separation of insolubles; removal of inorganic cations; and separation of the 2-keto-L-gulonic acid.

Abstract: A process for the preparation of vinyl chloride homopolymer and copolymer pulverulent powders suitable for the preparation of plastisols with improved rheological properties, comprising polymerizing to form a vinyl chloride homopolymer or copolymer latex and drying said latex by atomization, the temperature at which the latex to be subjected to drying by atomization is employed being at least equal to 40.degree. C. and being lower than the degradation temperature of said homopolymer or copolymer, and the resultant vinyl chloride polymer pulverulent powders.

Abstract: A vertical autoclave for carrying out operations involving a medium having a liquid phase and/or a solid phase, comprising:(a) a concave autoclave bottom;(b) a shaft along a vertical axis of said autoclave, said shaft passing through said bottom of said autoclave; and(c) stirrer means for driving said medium with a centripetal motion about said concave autoclave bottom.

Abstract: A vertical autoclave for carrying out operations involving a medium having a liquid phase and/or a solid phase includes:(a) a concave autoclave bottom;(b) a shaft along a vertical axis of said autoclave, said shaft passing through said bottom of said autoclave; and(c) stirrers for driving said medium with a centripetal motion about said concave autoclave bottom.