Mutations in the Drg1/RTP/Rit42 gene are commonly identified in hereditary neuropathies of the motor and sensory systems. This gene was also identified as a p53 target gene and a differentiation-related, putative metastatic suppressor gene in human colon and prostate cancer. In this study, we show that the Rit42 protein is a microtubule-associated protein that localizes to the centrosomes and participates in the spindle checkpoint in a p53-dependent manner. When ectopically expressed and exposed to spindle inhibitors, Rit42 inhibited polyploidy in several p53-deficient tumor cell lines and increased the population of cells in mitotic arrest. Blocking endogenous Rit42 expression by small interfering RNA in normal human mammary epithelial cells resulted in the disappearance of astral microtubules, and dividing spindle fiber formation was rarely detected. Moreover, these cells underwent microtubule inhibitor-induced reduplication, leading to a polyploidy state. Our findings imply that Rit42 plays a role in the regulation of microtubule dynamics and the maintenance of euploidy.

Separation of magnesium isotopes was investigated by chemical ion exchange with manganese (IV) oxide using an elution chromatographic technique. The capacity of manganese (IV) oxide ion exchanger was 0.5 meq/g. The heavier isotopes of magnesium were concentrated in the manganese oxide phase, while the lighter isotopes were enriched in the solution phase. The glass ion exchange column used in our experiment was 35 cm long with inner diameter of 0.2 cm, and 1.0 M CH 3 COONH 4 solution was used as an eluent. The single stage separation factor was determined according to the method of Glueckauf from the elution curve and isotopic assays.

Separation of magnesium isotopes was investigated by chemical ion exchange with manganese (IV) oxide using an elution chromatographic technique. The capacity of manganese (IV) oxide ion exchanger was 0.5 meq/g. The heavier isotopes of magnesium were concentrated in the manganese oxide phase, while the lighter isotopes were enriched in the solution phase. The glass ion exchange column used in our experiment was 35 cm long with inner diameter of 0.2 cm, and 1.0 M CH 3 COONH 4 solution was used as an eluent. The single stage separation factor was determined according to the method of Glueckauf from the elution curve and isotopic assays.