ROCK and mDia1 antagonize in Rho-dependent Rac activation in Swiss 3T3 fibroblasts

The small GTPase Rho acts on two effectors, ROCK and mDia1, and induces stress fibers and focal adhesions. However, how ROCK and mDia1 individually regulate signals and dynamics of these structures remains unknown. We stimulated serum-starved Swiss 3T3 fibroblasts with LPA and compared the effects of C3 exoenzyme, a Rho inhibitor, with those of Y-27632, a ROCK inhibitor. Y-27632 treatment suppressed LPA-induced formation of stress fibers and focal adhesions as did C3 exoenzyme but induced membrane ruffles and focal complexes, which were absent in the C3 exoenzyme-treated cells. This phenotype was suppressed by expression of N17Rac. Consistently, the amount of GTP-Rac increased significantly by Y-27632 in LPA-stimulated cells. Biochemically, Y-27632 suppressed tyrosine phosphorylation of paxillin and focal adhesion kinase and not that of Cas. Inhibition of Cas phosphorylation with PP1 or expression of a dominant negative Cas mutant inhibited Y-27632–induced membrane ruffle formation. Moreover, Crk-II mutants lacking in binding to either phosphorylated Cas or DOCK180 suppressed the Y-27632–induced membrane ruffle formation. Finally, expression of a dominant negative mDia1 mutant also inhibited the membrane ruffle formation by Y-27632. Thus, these results have revealed the Rho-dependent Rac activation signaling that is mediated by mDia1 through Cas phosphorylation and antagonized by the action of ROCK

Kinetic studies on the cationic polymerization of tetrahydrofuran under high pressure

The cationic polymerization of tetrahydrofuran initiated by triethyloxonium tetrafluoroborate has been studied kinetically at 0℃ up to 2000kg/cm^2. The course of the reaction was followed by the thermal method, and the rate constants for the elementary reactions were determined. The volumes of activation for the initiation and propagation reaction were -5.0±1.9 and -10.5±2cm^3/mol in the region from 40 to 1000kg/cm^2. respectively. The volume change for the polymerization was -7.9cm^3/mol, and the Volume of activation for the depropagation reaction was calculated to be -2.6±2cm^3/mol

Safety and efficacy of high-dose cytarabine MEAM therapy and other treatments for auto-peripheral blood stem cell transplantation: A retrospective comparative study

202