The application of dimethyldioxirane for the selective oxidation of polyfunctional steroids.

Oxidation and epoxidation reactions of a series of structurally different steroids related to methyl 5 beta-cholanoates having hydroxyl groups and/or double bonds by treatment with dimethyldioxirane (DMDO) are described. Steroidal alcohols, olefines, and unsaturated alcohols and conjugated enones with DMDO were transformed into ketones, epoxides, and epoxy-ketones, respectively, in good isolated yields. The regio- and stereoselectivities for DMDO reaction differing from those observed for organic peracids, tert-butyl hydroperoxide and alkaline hydrogen peroxide are also discussed.

Interactions between cytoskeletal components during myoplasm rearrangement in ascidian eggs.

Ooplasmic segregation in ascidian eggs consists of two phases of cytoplasmic movement, the first phase is mediated by the microfilament system and the second is mediated by the microtubule system. Recently, two novel proteins, p58 and myoplasmin-C1, which are localized to the myoplasm, were suggested to have important roles in muscle differentiation. In order to analyze the molecular mechanisms underlying ooplasmic segregation, the interactions between actin, tubulin, p58 and myoplasmin-C1 were examined. During the first segregation, microtubule meshwork in the unfertilized egg disappeared. At the second segregation, a novel structure of the microtubules that extended from the sperm aster and localized in the cortical region of the myoplasm was found. Moreover, uniform distribution of the cortical actin filament was observed at the second segregation. During the course of myoplasm rearrangement, p58 and myoplasmin-C1 are colocalized and can form a molecular complex in vitro. This complex of p58 and myoplasmin-C1 is a good candidate for a cytoskeletal component of the myoplasm, and is likely to be involved in the correct distribution of cytoplasmic determinants.